I use http://www.bmwmercedesparts.com/partlocator/index.cfm?siteid=215771 exclusively. They are a OEM dealer and are much less than my local BMW dealer. For example, called local dealer on an oddments tray to replace my ashtray...local dealer wanted $72. Husker BMW wanted $23 for the exact same part. I have ordered quite a bit over the last year and all their parts are OEM.
Those are good prices. I looked at rotors 34116855153 list 84.82 getbmwparts 67.86 bmwmercedesparts 58.99 I wonder how different their shipping is?