The home button on my iPhone 4 was shady at best. Sometimes it would work without any problems and other times I could click it 20 times before anything would happen.
The repair was lengthy to get the phone apart, but the reverse process was very simple and went off without a hitch. The only problem I ran into was the amount of glue holding on the glass front. In order to get any leverage to pry the front away from the metal case, I needed to give the front a little push from the inside. I obviously chose the wrong tool for the job and ended up with a small scratch on the back side of the glass that removed the black paint. Nothing a little sharpie couldn't fix, but a minor, whoops!
Patience. If you happened to have an early iPhone 4, it will have a stupendous amount of glue on just about everything. Be patient with taking off the front screen and careful not to scratch the inside where the QR code is located. Although it is tempting to push the front away from the metal frame, you will likely end up scratching off the black paint, which will show through on the front of the phone.