I bought one, and it did not work at all. Then I made a reclamation, and got a new one. It works great. Buttons are ok, what I have used em, not too fragile, working after few with hasty/too powerful push with foot.
Doesen't need a 9V battery to function, but it really helps on figuring what's goingin' on... Battery also last's for ever, since there's nothing but few led's using it.
It's a good buy, for a specific use.