The sound is phenomenal, particularly the low pizzicato. The stock strings it comes with are not really meant for arco playing, but it's easy enough to put whatever string you like on.
There are some design choices I would tweak: a faster way to switch between arco and pizz pick-up settings would be nice (the in-between setting is a fine compromise, but it's not the same).
The lack of body, ribs, and neck heel means there are no physical reference points on the instrument. As an upright bassist, that makes intonation in the middle register a bit dangerous. They do make a thumb stop attachment, but that has it's own problems.
Finally, this thing seems to eat batteries. If you leave the cable plugged in overnight, a new pair of 9v's will be necessary. I used to think that was a myth, but it's absolutely true. This bass is active-only, so dead batteries = no sound.
Despite these few drawbacks, this is still the best EUB on the market today. The sound quality is powerful and rich, and at the end of the day that's what it's all about.