I too recently finished off part of my basement (no room for a dedicated home theater though -- too small for that), and I too did just about everything myself except for the carpet. I really wish I would have hired out the drywall mudding and taping. No matter how hard I try, I never wind up with a finish that I'm totally happy with, so that was a great idea you had.
Can't wait to see the pictures of the finished project!
M60's VP150 QS8's HSU STF-2 Onkyo TX-SR805 Audiobytes for the PC