Feature:
Two features: a) You can clamp it down to any surface (meaning you can clamp it down to a tuba's rim, a classical guitar, a autoharp, a zyther etc.) and it will pick up the note you're playing by picking up the resonant frequency the surface vibrates at. b) Has felt covered clamps so you don't have to worry about it marring the surface of your "precious" instrument.

Quality:
Says Korg on the clamps and seems pretty well made. I would have liked to have seen a thicker cable cord though.

Value:
They don't make many contact tuning mics so compared to others in the same league they are priced just right and work like they should.

Desirability:
Nothing sexy about it. If you want to tune without all the mucking about with mics or acoustic pickups this does what you intended to do easily, tune without micing or pickup installation.

Sound:
Doesn't produce any sound... which is the reason I bought it. You can tune your non-electric instruments easily that way.

Ease of Use:
Doesn't get more straightforward than this, simply clamp-on, plug in and start a'tuning with your tuner.

Support:
Never had to use support.

Overall:
Does what it means to do very accurately and without much fuss. You can literally stick it anywhere and it should give you a reference tone you can use with a tuner.