I've used the Sonuus a bit. I got mine mostly for recording as I used to find some things easier to play on a bass than on a keyboard. Even in a controlled studio environment with the possibility to do more or less unlimited takes there was usually still quite a bit of MIDI cleanup required for a perfect result. Forget about slides, bends, popping, slapping, long sustaining notes or fast playing unless you REALLY enjoy spending time with a MIDI editor. Moderately fast playing and trying to keep overtones to a minimum was the key to success. Which basically meant it worked fine for some songs/genres but completely useless for others.
For playing live... I wouldn't trust it for any solo parts unless you don't mind unpredictable glitches. I guess the tracking might be good enough to work acceptably for a live bass in a dense mix... but I would make sure no-one does a recording of the gig.
Basically it's a fun, reasonably priced but also flawed little toy. I don't regret buying it but mostly because it made me realize I needed to improve my keyboard playing. Which I did and now the Sonuus is gathering dust.