I haven't had a chance yet, but I'll do basic stuff like oil changes. All the scheduled stuff will go to the dealer though. I mean, I get free maintenance (including brakes), so why waste it?
I think the overwhelming majority won't touch their cars and wouldn't know how either. While BMW used to be an enthusiast's car, unfortunately it's become just a status symbol. On this board, you'll still see the enthusiasts, but most BMW owners wouldn't join an internet board to talk about their cars since they only bought the car for the blue and white badge.