Bluetooth makes this insanely great!
I have both the 61-key and the 25-key versions of this controller, and I think Korg have done a very fine job. The feel of the keybed is, of course, a very subjective issue, but I find it to be at least as good or better than other mini-key controllers. Superior certainly to the iRig Keys or Xkey, which I also have. It is important to know that the 25-key version is slightly different from the other three in that it has no sustain pedal jack (why not?) and instead has a sustain button as well as an arpeggiator button, if you're into that kind of thing. Importantly, it also has the Korg joystick (which is also clickable), while the other three sizes have pitch and modulation wheels. Lots of setup parameters can be set using an editor that Korg provides, but this controller is quite intuitive out of the box.
Bluetooth connectivity is VERY cool and liberating; it's so fun to be able to go anywhere on a stage or in my classroom and play this controller. A minor grievance is that a few steps have to be taken to set up the connection every time you use this (or any BT) controller. You can't just turn it on and start playing whatever app you have launched. Not a big deal, but if you're in the third band of the night and the schedule is slipping, or if you suddenly have an idea and want to get your gear out and lay it down asap, any extra steps are annoying. Latency is very low, though it does get slightly longer as the controller gets farther from the device it's controlling. You would only notice this on a sound with a very fast attack, but some people are quite sensitive to latency, so it's something to be aware of. Overall, this is an excellent product in any size, it's a ton of fun to use, and I highly recommend it.