There really isn't anything wrong with it. Its kind of like a standard 91 without the flash hider, and what should be a better trigger. It does not have the nicer stock or pistol grip though. The higher dollar ones like the SR9T and SR9TC will have that. Those are the ones you see sell for like $4000.
There is some good info about the differences and why the SR9 exists here.
http://en.wikipedia.org/wiki/Heckler_%26_Koch_SR9