It's interior mexican food, served tapas style (basically, small portions). The guac is made fresh in front of you, and they offer about 100 tequilas to make fresh margs with.
Try the mole poblano (chicken with peppered mole) ... the lamb ... the carnitas ...
Huh. The one thing I truly miss is interior Mexican food...and anything with any reasonable amount of spice. I'll never understand the lack of heat in the cooking out here (Indian, Thai, Mexican, etc)...
I have been to a couple of real good restaurants there recently...
NOPA - A bit away from the Financial District, over in... well.. NOPA. The food was trend, but solid. The flatbread pizzas were an excellent starter. I had pork chop and it rocked. Our doorman at the Palomar recommend this and did us right.
Jeanty at Jack's is awesome if you want a historical restaurant -- oldest in the city. It's on Sacramento.
Park Chalet is great for the view and the beer. You get the beach and a decent micro-brew list. The steaks were above average and they had some good seafood offerings.
I used to live in SF. I really loved Bix on Gold St. Great jazz music, atmosphere and phenomenal food. I second Slanted Door. Le Colonial in Union Square is less expensive, and really good as well. I miss SF restaurants.