Yeah, I've been GPU mining on a gaming rig I built in January, with a Radeon 7850 installed. I have just about mined 1.3 BTC altogether using bfgminer on Eligius' pool, though I'm starting to wonder if I shouldn't be getting better than the ~250MHs I generally get. Not sure how to make it more efficient though.
Like Aztec said, it's been fun as a hobby, and I've been able to turn the first .6 I mined into about 1.2 BTC playing poker on SealsWithClubs, and with the prices soaring, I'm pretty happy to have about 2 BTC to my name.