I have Thule roof mounted ski and bike racks; These use the same roof rails, but the bike & ski racks are separate pieces. The Thule works pretty well, but can be aggravating to put on the car the first couple of times - even now, with practice, it can take up to 15 or so minutes. Roof mounts tend to generate lots of wind noise (duh), and I've found that friends with hitch mounts are a bit quieter. I've been thinking of getting a luggage pod like the one on shanek's car, don't know whether those come in hitch mounts.
1989 325iX 5spd Coupe Koni Adjustable/H&R
1989 535i 5spd Bilstein Sports/H&R, Tri-Flo, Conforti, UUC SSK
"If it isn't Diamondschwartz, it isn't... Dark Grey?"