It takes a lot of men to make a gun
Many men to make a gun:
Men in the mines
To dig the iron
Men in the mills
To forge the steel,
Men at machines
To turn the barrel,
Mold the trigger,
Shape the wheel--
It takes a lot of men to make a gun...
--The Gun Song, Assassins
Now, here's where I may get in trouble with a few folks. Some people seem to regard the basic 1911 design with an uncritical awe. To their minds, the 1911 represents handgun perfection; it is without flaws -- without flaws, you hear me? Any criticism of the gun threatens their perceptions of the universe. Meanwhile, back in reality, the basic 1911 is an antiquated design and it is far from perfect (sacrilege, I know). Come on, folks, if John Browning was alive today, do you really think he'd be designing guns like the 1911? Hell no, (Actually, Browning had moved far beyond the 1911 by the time he died in 1926. In his prototype for the Browning Hi-Power, already completed at the time of his death, he did away with many of the flaws of the basic 1911 design.)
Without trying too hard, I can think of four flaws in the basic 1911 design that range from moderate to serious. Several areas of the gun are prone to small-parts breakage; In some cases, when these small parts let go, the gun is totally disabled and it'll take a pistolsmith to get it back up and running.
A portion of the slide stop projects into the mag well for the purpose of engaging the magazine's follower and locking open the action when the gun is empty. Unfortunately, this also puts the slide stop almost in the path of a cartridge coming out of the magazine. Since the slide stop is only lightly spring-loaded into the down position, if a round of ammo nudges this part during the feeding cycle, it can pop up into the slide stop notch, locking the slide back with rounds still in the gun. This can get you killed. This malfunction usually occurs, if it occurs at all, when firing the gun with hardball and less commonly with shorter hollow-point rounds. If this hasn't happened to your gun, you probably have nothing to worry about; it's only a problem on certain guns. If you do have this problem, a good pistolsmith can dimple the slide stop where it touches the spring-loaded plunger. If the work is done to perfection, the slide stop will never pop up on you, but will still operate perfectly to lock open the empty gun.
The amount of pressure a 1911's extractor places on a cartridge casing's rim is regulated by the curvature of the part in its channel through the slide. This is a crude system. Too much curvature means too much pressure, and the extractor will not allow a cartridge casing to slip up into place, resulting in a failure to feed. Not enough curvature means insufficient extractor tension, resulting in failures to fully extract and/or eject. Most modern firearms use spring-loaded extractors, a far more durable and reliable system. This is a major improvement in firearms design that seems to have passed by the 1911.
The tension of a 1911's extractor can weaken with use. One sure way to screw up your extractor is to drop a round into the chamber with the slide open then drop the slide on the chambered cartridge. This will force the extractor to bend back and around the case rim, eventually abusing the extractor so much that it will lose its tension or even break off in extreme cases.
The barrel bushing/recoil spring plug is a high-stress area of the gun. Not only does the barrel whack around in the bushing every time you fire the piece, but the full force of the recoil spring also bears upon the bushing via the recoil spring plug. If the barrel bushing gives way, your recoil spring and recoil spring plug will depart the front of the gun at high speed. Effectively, the gun is disabled. Now, this doesn't happen very often, but I have had it happen to me while firing a Combat Commander. The bushing shattered, losing the semicircular piece that holds the recoil spring plug in the gun. My recoil system was somewhere down range, my gun out of action. I believe this occured because the slide of my gun came from the factory slightly shorter in front than it should have been. There was a fingernail-size gap between the barrel bushing's flange and the slide; you could move the bushing back and forth with your fingertips. This being the case, of course, the bushing took a hellacious pounding as it jacked itself back and forth every time the gun was fired, and finally it gave up the ghost. You should check your gun to ensure that the bushing fits snugly into the slide.
The exact same problem can occur from a different cause: The recoil spring plug may give way. This is common with hard use of the compact Officer's ACP guns. Most compact 1911s slavishly copy the Officer's ACP's recoil system, so this problem is not limited to Colts. On the Officer's ACP, the only thing holding the recoil spring plug in the gun is a tiny tab that hooks into a slot in the slide. If that small tab gives way (and it often does), your gun is hors de combat by virtue of a missing recoil system. I'm a big fan of the aftermarket recoil spring plugs for Officer's ACP-size guns that use a ring of metal at the rear of the plug to hold it inside the slide. There's no way such a part can come out of the gun.
The plunger tube that runs between the slide stop and thumb safety is a notorious weak spot in the basic 1911 design. This tube contains two little plungers and a spring, the power of which serves both to hold the slide stop in the down position until operated by the follower of the empty magazine as well as to hold the thumb safety lever in the safe or fire position. This is a high-stress area of the gun; every time you flip your thumb safety on or off, you apply force to the plunger tube. Unfortunately, the plunger tube is held to the side of the gun only by two small studs that pass through holes in the frame. It is not at all unusual for one of these studs (almost invariably the rear one) to snap off. I've had this happen myself while shooting, and I've seen it happen to other shooters. When this happens, your thumb-safety lever will wind up in a half-on/half-off position. In an emergency, it would be possible to physically hold the safety lever down in the fire position and still shoot the piece. However, for all practical purposes, the gun is disabled until the plunger tube is replaced.
There's really nothing you can do about this problem except to keep a close eye on your gun's plunger tube for signs of looseness. Some folks say that if your plunger tube is loose, you should simply have it restaked. I don't know about that. If the plunger tube has been loose for any amount of time, that rear stud has probably been abused enough that I'd probably feel better myself simply replacing the tube with a new part.
So, there's a lot to know about the ol' 1911, huh? It's not exactly the simplest or most maintenance-free design out there. The trick here is to enjoy the 1911 design for its strengths, but at the same time don't deny its weaknesses. Let me summarize my advice to maximize your 1911 auto's reliability: Load it with good hollow-point ammunition featuring a feed profile as close to hardball as possible. Use only top-quality magazines. Keep the gun clean and well lubricated. Check your bushing's fit in the slide. Regularly check your extractor tension and the plunger tube staked to the side of the gun for any looseness. If either of these areas shows problems, move instantly to rectify them.
Modifications? Leave the gun as stock as possible. If you must customize, do so with extreme moderation. Either leave your hammer/sear alone or, if you must have a trigger job, let only a shop that knows what it's doing modify this critical area. If your slide stop is popping up, have the slide stop dimpled by a competent pistolsmith. On the small, Officer's ACP-size guns, replace the stock bushing with an aftermarket bushing designed to stay in the piece. Let only the best pistolsmiths touch your gun. I like to put my preferred sights on a 1911, but that's a matter of personal preference and not an absolute necessity. And that's about it.
You in the front row....yeah, you with your hand up. You have a question?
"So, you're saying that you've got to know the 1911 inside out to get the best out of it? You've got to know what ammo to feed it, buy good mags for it, know how the various parts work and know where the weak points are in the design so you can have advanced warning if anything's about to let go. Is the gun really worth all this effort?"
Emphatically, yes; the 1911 is worth it. The 1911's overwhelming virtue is how easy it is to shoot. Quite simply, the 1911 design gives us the shortest, most controllable trigger pull of any handgun. In this area, all other one-hand guns must take a back seat to the grand old design. In my recent article on the easiest handguns to shoot, the Colt Government Model outshot several of the more modern designs, placing third out of five guns I tested. I believe it might have placed even higher, but I was determined that all the guns in my shootout be as stock as possible, so before testing the Government Model I replaced the excellent wooden Spegel grips the piece normally wore with the rubber wraparound grips that had come stock on the gun. The rubber wraparounds really bulked up the grip, changing a gun that had fit my hand wonderfully well into a gun that didn't fit my hand at all. The fact that I was still able to fire the piece well is, I feel, a tribute to the Government Model's inherent shootability.
Another thing I like very much about the 1911 is that it's the only serious, heavy-duty combat handgun out there that can be totally detail stripped without tools. Not to get too Zen here, but when I know I can totally disassemble my carry gun and put it back together again using nothing but my own hands, it gives me a wonderful sense of being one with the gun.
No, the 1911 is not a gun for the casually interested. However, for the dedicated shooter who's willing to take the time to get to know the design intimately, the 1911 is still a superior choice in a defensive handgun. Unlike most things in life, the 1911 has strengths that more than compensate for its flaws. If it's not perfect, well, what is?? 
This essay is longer in-game than the text here. It's actually a bit over 4000 words.