Just got one today, and I gotta say, it's really impressive - let alone for $350. First thing that surprised me is that it feels really substantial - the bottom is metal, not plastic, and the top and sides feel really high quality. I expected it to feel extremely cheap and plasticky.
The action itself is semi-weighted and fast, but still has a nice bit of resistance and bounce to it - it doesn't feel like empty plastic. Having had surgery on both hands last summer and still dealing with some pain when playing heavy weighted actions, this is exactly what I was looking for until I can get back to a heavier action. And frankly, I can imagine ending up with this permanently given the need for 88 keys but without a heavy, slow action. Oh, and it has pitch & mod wheels even if they're top left rather than beside the keys where they belong. And finally, all the pads, buttons and faders are a nice bonus and feel decent.
If I'm nitpicking, you can't adjust velocity curves onboard - you need their app for that, and the curves aren't editable. Further, none of them is perfect for me, so I'll need to create a MIDI transformer in Logic to tweak to taste. Also, the white keys are 5.5" rather than the full 6", but easy to adapt to. For whatever reason, every semi-weighted action I know of is like this. Last thing: the front edge of the "lip" on the white keys is a bit sharp - could be smoother.
All things considered, I think this is the controller to beat right now for my $$$!