I've fixed about a half dozen so far, with various issues. They aren't too bad, but you need to take your time and remember everything you did so you can do it all in reverse. I also bought my parts at DealExtreme, and while most are pretty good, they may not have the same feel / fit. I replaced a shoulder button in one of mine and it works fine, but it is quite a bit "squishier" then the other OEM part. Something to consider if that's important to you.
You might want to order a screw kit as well. The tiny screws are easy to loose, and the screw kits are pretty cheap.