As a standalone unit I can't fault the UNO, especially for the price. It has a nice feature set and range of sounds, the touch-keyboard is surprisingly good and it's very compact but also very usable.
I've deducted points for what seems to be bad MIDI implementation; I have issues with the synth producing no sound if the wrong thing is highlighted in the DAW (despite MIDI signal being sent to the UNO), the arp won't trigger via MIDI, and so a lot of what I wanted to use it for I just can't. It could be a faulty unit, but I never got a response to my customer service ticket to IK, so I don't know. Based on my experience I would also rate IK's service at zero stars.
In addition, the supplied USB cable is pathetically short and it is quite picky in terms of using an alternative; I tried several cables before finding one that would work and it doesn't like USB passed through an intermediate device.