Depends on how much you plan to do with it. Are you just considering doing the framing, or will you be framing and finishing? If you are going to be putting up molding, it's hard for me to imaging doing that with a hammer and nails anymore. Of course, you have to have a finish nailer now. Will you be building fabric covered panels? If so, you're are looking at thousands of staples! The pneumatic guns seem to be the way to go.
I've already got a compressor, but I recently picked up a framing gun and most of my theater is already framed out. I decided it was worth it to me just to save the time for that last little bit. YMMV.