Slower - I've had BMW's since 2005, and I much prefer my local ind. shop to the dealer for post-4 year maintenance. Better prices, better quality of work. Go to your regional board (
http://www.e90post.com/forums/forumdisplay.php?f=46) to find a good independent shop.
I don't have a 335i (I have a 328i), so I can't speak to the reliability of your turbocharged powerplant.
Congrats on your purchase! Enjoy, and be safe on 128!