Works like a charm...
I took delivery of my 335 last week and just received the correct cable today. I live in Germany and got my car through the military sales program - it was the first one delivered with the 6FL, so there was a little confusion on the cables - be sure yours has the two-pronged cable with aux and USB at one end and the iPod connector at the other. Mine was delivered with just a short USB extension cable. The dealer told me that the cable will cost extra in the states, not sure if that will hold true, but she paid for mine and express mailed to me.
A USB thumb drive works fine - I used a 1GB stick I had while I waited for the correct iPod cable.
Now that I have the iPod cable, the whole thing works great - exactly like I thought it would. I don't have iDrive, so it takes a while to search through albums, artists, etc. but I usually just use playlists, and that works great.
Right now, no complaints at all - well worth a few extra hundred $$, IMHO.