it looks pretty cool, but I don't think it would be very useful for an arcade CP. Like Jakobud said, I think it would be very awkward. You'd have to mount it at the very edge of your CP so that you could retain some comfort. Either that, or you could build some kind of break out box into your CP that could be removed and used as a handheld controller for console emus. But frankly, if you go through all that trouble, just go buy a USB gamepad for 10 bux.
I'd be interested in playing around with one too, but I don't think they'd be much use to most of the CPs you see on MAME cabs around here.