...an accessory Picatinny rail for optics, easy disassembly, an ambidextrous safety lever, oversized trigger guard for easy operation while wearing gloves and a lifetime warranty. However, there is no magazine interchangeability with H&K or any other handguns.
My main complaints with the USC were the heavy and weird-feeling trigger, non-ergonomic safety lever and very poor notch-style rear sight. The rear sight was positioned too close to the eye for a clear picture with the notch, but the flip-up aperture was much better. While all the shooters agreed on this point, they also felt it was the most comfortable and fun to fire. The H&K USC was infallibly reliable with every load tested. It also looks pretty darn cool.