My agency issues Glock .40's and they are mandatory for all uniformed personnel and SWAT. I just recently got approval to test and evaluate the M&P, and it passed with flying colors. 2000 rounds, no malfunctions, good test scores, good feedback from the shooters. Now the Chief and I are carrying M&P's as we re-evaluate the needs of the agency. Back up guns are officer's choice of gun in .380, .38, 9mm, .40 or .45 but the most popular BUG is the S&W J frame. Investigators or other plain clothes officer can carry either the Glock 23C or a personal gun in 9mm, .40 or .45 if it meets inspection and they can pass the advanced qualifier with it. My Lead Detective carries an H&K45C but most of them carry the G23C. My M&P is my primary, but I also carry an LCP as a back up and am testing an LC9. I prefer 9mm and I prefer ergonomically friendly guns. S&W and Ruger fit the bill nicely. Take care.