Oh yeah -- this tiny place is the real deal. I've been to Japan twice and Ittyo totally reminds me of the no-frills udon and donburi shops I frequented in Tokyo. While I haven't tried everything on Ittyo's menu, I adore their unagi donburi (bbq eel on a bed of rice -- it's cooked very well and I've never had the nasty eel bone experience at Ittyo!) and kitsune udon (fried tofu in the traditional udon noodle soup). The servers don't necessarily speak English very well, but it doesn't matter -- the menu has clear pictures of everything, so you can just point to what you want. You have to pay cash, and with only 6 tables, you sometimes have to wait. But it IS worth it.
Pros: authentic Japanese, without pretentions
Cons: small (but cozy!)