I have one of the prototypes and its the Steel Challenge model. To be clear, its not mine, JP loaned it to me because I am writing a review of it for GunsAmerica. I have to send it back in a couple weeks.
So far it is fantastic. Worlds better than a blowback PCC. It had more push than an MPX but it does not really disturb the sights and its way way lighter than an MPX and more reliable from what I have seen so far. So far it has shot 18 stages, many testing sessions, roughly 800-900 rounds with no problems.