I've had one of these for ages and routinely use it for practise and band/orchestra rehearsals.

"All instrument" in that it will register a note for any instrument that it will pick up vibration from.

Transpose though is very much based on where you'd put a capo on a guitar and won't ever show the right notes for a Bb instrument. I still use it for my tenor sax - I don't really need to know what the note is!

Auto-off is also just a bit too frisky, so often turns off between pieces when I still want it on. Battery never seems to last that long either before the display starts to dim perceptibly.

So it's ok, "all instrument" is not wholly true, it's still usable/useful, but I rate my Korg tuner more highly (which I replaced because the battery holder broke).