I have a couple of them, and I like them ... when they work. I say that because I got two defective ones from
Sweetwater. Since getting past that little bump in the road, the two I own have worked great. They take the same 2032 battery that seemingly every other clipon tuner does, which is convenient.
Since the UniTunes cost a little more than the Snarks, at least IME, I tend to leave them home when I play a gig, usually taking a Snark instead (because I regard it as slightly more expendable). But it's not because the UniTunes aren't gigworthy; they are.