I think Gusto may be one of my favourite restaurants in the city. The ambiance is always so fun and boisterous but I don't find it too loud. You feel like you're part of a scene there and everyone seems to be having such a good time. That may be the $1/oz wine on tap - which is not bad at all! The rooftop bar patio is a great place to spend a summer apres work.
I don't love the no reservations thing but I believe for a larger group there is some accommodating.
For food, I love the kale salad and I'm not generally on the kale bandwagon, the spinach pizza with ricotta is fantastic, bolognese is rich and filling in a good way, and the meatball pizza is a nice change to the usual salami. For lunch I also like having the kale salad with some shrimps or chicken on the side.
Sister restaurant Nervosa in Yorkville is equally good food but the environment is lacking in comparison.