My home button was not working well, but not completely broken either. It would work fine for a while either after several attempts or if I was within the walls of the Apple store. The button felt just a little 'crunchy' but I had no warranty left, and I already had my complimentary repair on a shattered back glass panel (during which the home button worked just fine). I found this guide and selection of parts here on iFixit and decided to take a leap of faith and do it myself. I figured if I messed anything up, I'm eligible for an upgrade to the 4s.
Thanks to the detailed guide it went just about perfectly. I organized things by printing the guide out on paper so that I could tape each screw to it's exact spot in the photo as I went through the steps, but kept a laptop handy to be able to zoom in on the alternate views. Having the right tools on hand boosted my confidence that I wouldn't scratch or break anything.
The tear-down was a cruise. Everything was just as described in the guide and when I got to the last step I could see a ring of gunky looking corrosion around the base of the home button so I knew I was replacing the right thing. The return trip was where I made my only mistakes and took quite a bit more time. Ultimately, I made my way back to the start with a fully intact phone and no extra pieces left. I held my breath for the moment of truth of powering up, nearly had a heart attack during those brief initial seconds when the passcode lock keys are somewhat unresponsive, then did my happy dance when it worked and everything tested perfectly. It's been like having a brand new phone now. The home button just needs a nice soft touch and I'm no longer hesitant to use the multi-tasking features.
One of the main things I was worried about was that my phone might have a slight rattle due to weakened glue, or fingerprints under the glass or something like that, but the way these things are made, I can't even tell that I've done anything to it. I'm also very confident that I can fix just about anything else that iFixit sells parts for now. There went the only reason not to Jailbreak.
The step where it tells you to make sure the ribbon cables for the earpiece and the digitizer (that are kind of piggybacked) aren't pinched when you put the front panel back on the case... Yeah, make sure you look over at the logic board how the sockets are arranged and make sure the earpiece ribbon cable comes down far enough. That's the one that gets pinched and it's not obvious until you get all the way to the step of reconnecting them to the board. I made this mistake, but escaped without damages because I slowly worked my way all the way back to that step instead of trying to pull the ribbon cable free.
When you put the speaker enclosure back in, check for the little antenna cable and make sure it's not pinched underneath. You won't be reminded of it until you get to the step of reconnecting it.
Lastly, when putting the camera back in, mine didn't go in flat and flush at first. It seemed nice and tight, so I proceeded even though I wasn't sure. Turned out it was wrong, so I had to roll back to that step and then reseated the camera, this time leading it in at an angle so that that side that was higher the first time around went in first. That took care of that.
Do come up with a plan for screw management. Buy the magnetic pad they have here or do like I did and tape them to their label. I don't think even using containers to separate them would be a good enough solution, there's just too many different ones and it's always critical that you use the exact right one.