gotta give a 3rd to BITE on Bleecker and Lafayette. Try the turkey, swiss and pesto panini or the mozzarella, proscuitto, and sun-dried tomato panini. I posted a review of it (with pictures) on Roadfood.com under the "sandwich shop" category.
'ino is definitely the place. if you're looking for something casual and are willing to pick up and take elsewhere, i really liked the panninis at murray's cheese shop. have them pressed and take em down the street to the tiny winston churchill park and eat there.
There is a tiny kiosk called Bite on Lafayette/Bleecker - awesome and inexpensive. That's where I go when I get sick of sitting at the NYU library. The small place next door called Sparky's serves good comfort food, too.
I'll second Bite. The panini with prosciutto, fresh mozzarella, sun dried tomatoes, basil, and olive oil is fantastic. Grab a bench over on the Mulberry side (I haven't yet tested Sparky's willingness to share their Lafayette seating).