Trattoria nervosa is a favourite of mine, their staple of course being the mushroom pasta, and they know it.
As we were ordering, the server pretty much took the words out of our mouths, which I don't know if it is a positive or negative thing. Either way the pasta was delicious.
Even without reservations, I think we only waited about 35 minutes for seats, which, for what I consider top 3 restaurants for pasta in the city, fantastic.