I am going through this process right now for the first time. I went with intercity due to many positive recommendations. They cost a few hundred more but their reputation seemed worth it. I'll post more direct feedback when I get the car.
2011 E90 M3 - Alpine White/Fox Red Extended
Premium/Convenience/Cold Weather Package - Competition Package - M-DCT - Sunshades - EPS - BMW Apps - Sat Radio - Ipod/USB