I've never really had a problem in a bike store, even when I weighed 300. They're generally very helpful to anyone who's going to inevitably drop some cash every time he walks in. Like was stated above, helps when you ride in on your bike, nobody really looks at you funny when you're dressed like you mean it, and you have the paraphrenelia to prove it.
The only place I really get some funny looks are in some of the group rides. While most people (80-90%) are generally cool, some of these guys have egos that extend way beyond their dura-ace, and simply can't stand being behind you at any point whatsoever. It's fun to watch them kill themselves over this superiority complex, for no real gain whatsoever.