The home button on my iPhone 3GS stopped working, and the coating wore off so if you breathed near it, it would fog up.
It went very well, although even though i bought the phone new and never opened it before, there were some strange things that the factory (apparently) did/didnt do on the innards. There was an extra screw just sitting around inside the case, not missing from anywhere, and the reported black tape securing the digitizer to the screen also didnt exist.
I wore latex gloves, and was armed with compressed air and screen cleaner, and it helped very much to keep the grit and grease out of the inside of the device. The first time i put it back together i realized a hair got trapped between the screen and digitizer, so i had to re-dismantle and re-assemble it, after that all was well.