I use it for guitar setups - works well.
I like the roller ball thing for intonation.
Not sure about accuracy but I find the tuner to be too jumpy. It is very hard to keep it still in the middle. Maybe it's too accurate and therefor that jumpy? I never use the roller ball tuner. I don't really know how to handle that (just don't know when it's in tune) and therefor prefer the normal tuner. But it doesn't work as well for me as my Boss TU-2 or my Korg CA tuner.