I have a couple of favorite bike shops I really like and they are staffed with great people. No problems at all. Maybe being in the city that Fitness Magazine has stated is the most overweight (also the one where most people tend to eat out) makes the difference. Maybe a couple of times I've been ignored, but it's been a while.
When I get my Bushy Bux I'm planning on going bike shopping (gotta help the economy). I already know pretty much what I want. I'm leaning pretty heavily towards the Jamis Aurora, fixing it up for my commuter/randonneur bike (from one of my favorite shops). Maybe I'll hit a few shops I haven't visited before just to see what kind of reception I get. If it's bad, it would do them some good to remind them that overweight guys pushing really hard against 50 are serious cyclist too.