If you're getting good prices from 42nd St Photo it is almost certainly on gray market gear. If you're OK with that no big deal. If not, a deal that looks too good to be true probably is.

B&H is fine in person, but they are really looking to process sales more than kibbitz about your gear and talk for a long time. That effect is magnified on the phone, as those agents are expected to be processing a lot of orders all day long, not help you decide between the XTi and XSi and which lens(es) you should also get.

Adorama is similarly good to B&H (and closer to my apartment), though B&H has more gear on display that you can pick up and play with.