That's a really neat concept, it's an interesting trade-of, forcing you to move oddly and strafe a lot, especially since some weapons seemed to rely on which key you replace. Made some rooms quite challenging once I got the hang of it.
I had two issues, though. One, it's REALLY mean to spawn the *first* weapons in a hail of gunfire!
Two, shooting upward seemed to be very, very tough - it seemed as if the mouse angle determined if you shot up or not, and I had trouble with an upwards angle where socketbot would block my view, especially troublesome in the second level with all the devilbots on the buildings. I think I destroyed things mostly by change, and "won" more by running away than fighting.
I'm not a FPS/3rd Person shooter player, so maybe it's easier for those with experience with those genres and the feedback can be discarded. Just wanted to give it, in case it's of interest. ^^