Burris Fastfires are great for recreational purposes. I've been using the original Fastfire for several years on a Browning Buckmark and for a while I was using a Fastfire II mounted on an AK via a quad rail. The automatic brightness adjustment works very quickly, I'd go as far as to say immediately. These sights were designed to be mounted on handgun slides, and as a result, they will hold up just fine to any recoil forces that a USC or 94 would exert.
One glaring disadvantage is the overall robustness. I don't think they would fare very well to being dropped, accidentally smacked into a door jamb, etc.