I find only two Ame reports since mid-December and I think Hiro Sone (and his chef in SF) deserves a little more attention. Neither of the write-ups mention that this restaurant was started by Hiro Sone, the chef behind Terra in St. Helena.
The feel at Ame though, in the St. Regis Hotel right up the street from SFMOMA, is more modern / minimalistic and a bit austere, although the deep browns and high ceilings provide a warmth that is almost unexpected given the decor and the corner, ground-floor location of Mission and 3rd (the ceiling to floor length sheer curtains allow the blur of traffic and pedestrians to be a soothing rather than intruding element).
The food I found exquisite. Having eaten at Terra several times, I expected perhaps more of a French influence, but Ame's dishes are asian-skewed (the sushi-based selections should have been a clue to that - I'm not too sharp). My gf and I started w/ a selection from the sushi bar each, I had the cuttlefish noodles which arrived with a lovely piece of uni and raw quail egg and finely shaved daikon (I think). Clean and refreshing. GF had the Poke, which they wrap in seaweed and tempura very briefly before slicing. It was raw but partly warm and had that great spicey / soy flavor that took me back to my first experience of Poke in Hawaii.
I went w/ 2 apps, the Chawan Mushi (which included lobester and more uni) and the duck ravioli, rather than an entree (both were excellent) and my GF had the black cod with dumplings - the cod was beautifully grilled with that fatty-rich flavor and a slight ponzu taste from the sauce.
They have a good selection of sake and funky cocktails as well as pretty good wines by the glass and decent bottle prices (about 7-8 1/2 bottles in red and white). We passed on dessert - that's a long story, but I wish we hadn't.
There's also a little "sushi-bar" like area that you could sit at, so if you were solo or just wanted to try a couple bites, it would be very convenient. I saw a guy have the chawan mushi there as I left.
As noted by others, there is a pretty nice bar area / lounge as well, although it is detached from the restaurant at the entrance of the hotel.