The home button on my iPhone 4 was flakey. Apparently, a common problem. I was holding out for the iPhone 5 announcement, and was somewhat underwhelmed. Once I finally decided NOT to upgrade, I knew I had to fix/replace my home button. Since I was going to replace it, I was going to make my phone unique so I got a white button for my black iPhone.
I also picked up the transparent rear panel because, why not? I _SAVING_ money by not buying an iPhone 5, right? ;-)
Holy cats, the iPhone 4 was not designed to make it easy to replace the home button. iFixIt is NOT kidding when they rate that as 'Difficult.'
However, their instructions did not lead me astray. Following the guide got me to the home button with no surprises or extra work. Now my iPhone is a) functional, b) multi-colored and c) transparent!
Pulling the display from the metal case was a lot harder than they made it sound. It was basically as described, but the fit was so tight that the iPod Opening Tool didn't want to slip in there. I ended up having to sacrifice a bit of scratching on my phone and use a very fine metal screwdriver to get between the plastic gasket thingie and the metal frame.
I would also recommend the magnetic screw mat for the task. These suckers are TINY, and it's not always easy to remember which one came from where. $deity help you if you drop one or accidentally knock it out of the way. I didn't have the magnetic screw mat and wish I did.