I haven't fired one, but I did get a chance to handle a couple of them at the SHOT and NRA shows. Very light, the folding bipod is neat, and the whole things folds in half for storage. Accepts AR mags, which is obviously a very good idea.
However, based on its appearance and "feel," I'd guess it is strictly a light-duty carbine. It is mainly plastic, including the front sight and most everything else. Basically, it is constructed like Kel-Tec's fun little SUB2000 9mm/.40 carbine -- which is to say it will probably not survive hard use very well. The bipod would probably be the first thing to break, then the front sight assembly.
This isn't a knock on Kel-Tec (they make some unique and useful little guns) at all, since they don't intend their guns as military weapons. My sister keeps the SUB2000 in 9mm for a home defense piece. It's reliable and easy to shoot well. I'll bet the SU16 will be about the same, and be well suited for use as a fun plinker and light-duty home defense gun. Probably be neat in the truck/trunk gun role, too, so long as it isn't subjected to many hard knocks.
Mike