I was plagued for a couple years with a vibration on acceleration...FINALLY figured out it was the driveshaft. This was after I replaced the rear wheel bearings, shocks, CV driveshafts, center driveshaft support bearing, and the guibo coupler at the trans. Talked to a GREAT company out of Portland, OR called Driveline Service of Portland.
These guys were awsome, and I had a new driveshaft ready to bolt on shipped all the way to me in Ohio for about $400. And, they have a better warranty than BMW.
Took out the old, installed the new, vibration GONE.
Check them out here: Driveline Service - Driveshaft Specialists