Funny, I live actually fairly close to Japantown; it's pretty nice. I've only been once, because I tend to be rather busy, but it is fucking awesome.

Japanese restaurants, like everything else in SF, tend to be expensive, and there tend to be two types of Japanese restaurants: sushi bars (most common) and proper 'Japanese restaurants'. The proper ones are a bit more expensive, but. And if you're looking for restaurants, the locally owned places are the most awesome.

Anyway, I'm glad you're having a great time! Being a 'local', I don't often get to see the 'touristy' stuff as much as I'd like, so it's alwas interesting seeing things from a different perspective from 'aaaah, Japantown, I ride by it on the bus all the time.' :P