I use a few of them depending on what I need done and where I happen to be. I agree that Rusnak is one of the most professional. It's a little far from me, but the ride isn't all that bad.
Santa Monica BMW is really close to me, so I use them for quick things like oil changes and they've always been easy to work with - but if it's anything that requires leaving my car overnight I can't use them since they only issue loaners if you bought your car there. I bought mine at Pacific but their service department can be a hassle to deal with so I usually avoid them.
2013 750i Mineral White
2011 750i Jet Black
2007 750i Monaco Blue