This is my first ever build, and as a result, I did a TON of research (and lots of posts to Tom's Hardware).
I'm not really a gamer, though I play a game here or there, but I think this thing would do great with most that I'd throw at it.
I wanted something that would be able to do some basic HD video editing (using Sony Vegas Movie Studio HD Platinum 11.0) that would keep up with all the media my wife and I bring in with all the HD captures we do now. Also wanted something that will last a few years. I threw in the Hauppage TV tuner card for converting old VHS tapes through a VCR hooked up to it, which, using just Windows Media Center, seems to be working now (have to juggle a few things around).
Pretty smooth running build. A LOT quieter than I anticipated, having 6 case fans in there and two on the CPU; I actually have it sitting in the standard computer bay under my desk and it keeps plenty cool (though I did take off the front door). I really like that case too; plenty of room, and like the hot-swap dock on the top.
Prices were what I paid for each item after rebates, so look for those rebates when you're researching!