I like Patelson's. I generally don't bother with anyplace else, now that G. Schirmer's has followed the pattern of most other things of enduring value in this country and closed up shop.
They are a bit light on organ music, however. Teddy Presser in Bryn Mawr, PA has what seems like most of an entire large room devoted to organ music, at least the last time I was there in 1990's. Patelson's has basically just one medium-sized wall of shelves up on the mezzanine. It's still a decent selection, mind you, but I think they should try to do a bit better--especially now that they have essentially no competition in town.