Much like Agency Arms and Head Down, etc. do to a Glock, adding serrations, edges, stippling, etc. to enhance the pistol, Smith and Wesson is having none of it. In fact they recently sent a cease and desist letter instructing a gunsmith to stop customize the M&P as it was both infringing upon the design and trademark as well as safety concerns.
Personally I believe this is a bad move on S&W part and makes them look like a jealous ex-girlfriend.
http://www.recoilweb.com/sw-sends-cease-and-desist-letter-to-custom-gunsmiths-80507.html