Difficult installation made much easier with iFixIt photos
My iPhone 4 is now over two years old and the home button was starting to go. I often had to press it 2-4 times for a "single click" and 4-8 for a "double click".
This repair is a pain to do unless you have experience, BUT the directions are great and it's a lot cheaper than buying a new phone. As a bonus, at the end of the installation, you have taken apart the entire phone, so future repairs will be much easier. For example, I could now replace the battery in <2 minutes.
Problems I ran into: 1) My phone was missing a screw on the battery cable, though I have never taken it apart before... 2) A few small parts that were glued on FELL OFF. 3) The wifi antenna didn't work after I reassembled the phone.
How I fixed these things: 1) I couldn't do anything about the missing screw, but I have yet to lose power before or after the home button install. 2) I glued them back on, which didn't work so well, but the phone is functioning ok with these two loose parts. 3) I took the wifi antenna back off and reinstalled it. I don't know what the problem was, but it works now.
The photos in the step-by-step instructions were invaluable - especially for figuring out where the two rogue parts came from. The labels in each photo made trouble shooting easy- when I had my wifi problem, I knew exactly what part to look at.
I laid out each of the screws on a paper towel in their relative location on the phone, basically making an outline of the phone in screws on my table. The paper towel kept them from rolling off the table, and laying them out according to how they fit in the phone made it easy not to mix them up.