"H&K: Because you suck and we hate you"
Don't get me wrong, HK makes a good gun, but this is the consensus for a reason. The gun itself is fine, the problem is with the company, they offer poor customer service to both civilian and government agencies a like, making parts acquirement impossible.
And before you ask... yes, even HK(s) (or Glocks, 1911s, and Sigs) break at some point, requiring replacement parts.... If you haven't broke a part on a gun, then maybe your not shooting it enough.
One thing though, some guns tend to be more "durable" than others. I'm not saying that "gun x is more durable than gun y because it was dropped from a airplane and survived". I'm saying that some guns require less maintenance (not cleaning, talking about parts replacement). For example, it is encouraged to start replacing springs on a 1911 after 3k rounds, and maintain a consistency to do so. On something like a Glock, well you can think about replacing the spring once your slide starts to feel soft or you start having issues. I don't have the exact numbers for Glocks, but I can tell you, I've replaced more parts on my 1911, compared to my Glocks.
Blackadder pretty much nailed it on the head in the post above. Personally I wouldn't go as far as using a Tokarev, but that's him and the idea is sound.
What you will find, if you shoot a lot, is what attributes of a gun do "you" like. I don't like DA/SA triggers, so I lean more towards a striker fire system or a 1911. I also use a really high aggressive thumbs forward grip, so the placement of the slide release on Sigs don't work with me.
This is why it's common to hear "choose the gun that you shoot best" because at the end of the day, you are the weakest link in the system. Not the gun, not the bullet size, it's you. (disclaimer: this only applies to modern, reliable handguns. If your gun is un-reliable, then it's the problem)
Now how about some video? Long story short, an internet fight on a local forum I visit, started a big fiasco about the reliability of a polymer AR15 lower.... good news is that everyone contributed and I got to shoot most of the ammo! We fired 860rds over the day and this is some of the video from that. The upper is mine and it is a Noveske N4 Recce, the lower is the PLUMCRAZY polymer lower. The end result of the lower was that it did survive but had minor melting which could stem into bigger issues. At this time I really don't recommend these things for a serious use gun.
Yours truly, Nrose8989 shooting the steel!
http://www.youtube.com/watch?v=YZP1S-03FjE