I was momentarily tempted but the lack of format support -- specificaly ePub (DRM and non) -- and the memory of the eInk flash when it refreshes kept the impulse buy at bay. Plus I find the keyboard a waste of real estate. But... if this came out when I was first shopping for a reader I probably would have gone for the K3 over the jetBook.
If there was the ability to host my own server and pull my own books off of my local archive via WiFi they'd have me switching. AFAIK this doesn't exist and I'm guessing its hard wired to call Amazon only. Are you listening Ectaco?