I've had great luck with C & M, on 17th St.

http://www.manhattanvelo.com/

two times i've had repairs done and both times when i went in to pick the bike up, it turned out it was much less than they quotes -- in one instance, the bill came to $6.00. Just took a bianchi volpe in for a tune up for $50. And if they have time, they'll do what you need done while you wait.