It was pretty bad. I was fighting the API the whole time because its post-processed palm and finger positioning data was noisy and and error-prone, and it didn't have a raw mode. The API would frequently lose track of individual fingers. You also couldn't do any hand gestures that involved your palm pointing horizontally instead of up/down because it would lose track of your occluded fingers. It also had issues tracking fingers when you held them together (as if you were going to karate-chop something). It's just too many quirks to deal with if you're trying to do hand position and gesture input.

Maybe it's improved since then, but after one day back around the initial launch I basically gave up on the tech for hand tracking, deciding that it was just not a good approach.