I hate how my HTC's homescreen decides to unload itself after not using it for a minute or two. Every time I hit the home button I end up being unable to use the phone until it is done reloading anything.
Hitting the button on accident is a major pain, and beyond aggravating. It is especially annoying when you just want to do something that should be quick - like check the time or set an alarm!
I'm not saying it's androids fault, but one of the major problems I have is that developers (even HTC!) are given a little bit too much lee-way from the OS. Its one thing if an app is mis-behaving since you can just uninstall it (i'm looking at you facebook...). It's an entirely different problem if it's the homescreen.
That being said, the later version of the OS seem to handle this a bit more intelligently.