I have one. They're one of the best blowbacks you can get, IMHO. They operate unlike any other bb-the hammer and bolt are one piece and the valve is vertical. Instead of smacking the valve pin directly, a 45-degree shoulder on the hammer pushes the pin down as it slides by. The velocity is adjusted not only by mainspring tension, but there's also a choke screw similar to a Tippmann which you can use to fine-tune the velocity. There's also a screw to meter blowback gas so you can tune it for maximum efficiency. The quality seems much higher than most entry-level blowbacks as well.
Mine came with a eurogrip, which I had originally swapped out for a 45 frame, which ICD still has available. It's currently set up w/ a Lonestar grip. There's provision for vertical or backbottle. I have mine set up with a bottomline and expansion chamber. With a 14" DYE Ultralight, mine is one of the quietest guns I have. Even firing w/out paint it just goes 'thup'. I use it as my main loaner.