I've never bought a car from a dealer, and do all of my own maintenance, so my experience has been limited to the parts counters at three dealerships. One is Park Ave Motorcars here in Palo Alto, one is Autobahn Motors in Belmont, and the last is Smythe European in San Jose.
Of these, my favorite is Smythe European. I've only been there a couple of times (it's a half hour drive from here), but they've always been kind, courteous, and have gone out of their way to help me.
Autobahn is a close second, although one of their parts guys tried to sell me an oil filter for a 300E once...I wish more people knew the phonetic alphabet; that way I could just say "300 Delta" without people looking at me like I've grown another head.
However, I've had some relatively bad experiences at Park Ave. The people there tend to be rather snooty, and they always overcharge for parts compared to the other dealers. It's frusturating 'cause they're a 3 minute drive away.
I do try to get my parts from Fastlane, though, unless I need it in a hurry or the cost-to-ship doesn't justify the lower initial cost. I also get my oil filters from the dealer...but I do that with every vehicle; I used to get oil filters for the truck from the Ford dealer until I found out that Walmart has the exact same Motorcraft (Ford's OEM) brand oil filter for half the price...