I like it.
The food is relatively authentic: not completely, but more so then quite a few restaurants in the World Showcase (probably because most of us are pretty used to Japanese cooking, admittedly, but it's still nice). You're not going to find anything unusual there, as I commented in a sushi review, but there are some traditional dishes. The staff is beyond courteous: they're some of the most friendly, chipper and helpful cast member's you'll find at Disney. There's a relatively decent list of sake and sake cocktails, which is always good. And I've never had a bad meal there.
I don't usually end up making reservations for here, but if I suddenly get hungry in World Showcase and don't have something scheduled soon, I almost always end up at Tokyo Dining. Because Teppen Edo is so much more popular for the 'show' aspect, Tokyo Dining does usually see light crowds. You can almost always just walk in.