Hubs, bottom brackets, and headsets are, in my opinion, the most important parts for a commuter bike. I wouldn't go cheap on these. If I was building a commuter bike from scratch I would use XTR or Phil Wood hubs and BB, and a Chris King, Syncros or equally good headset. Any other parts (drivetrain, brakes etc.) I would get decent stuff but I don't think it's necessary to spend alot of money to get the best.