On my list of features rails don't even get an honorable mention. My S&W autoloader has them, big deal, it's just the way the gun was made. I didn't even notice it until after I had bought the pistol.
The only two things I can see that someone might want to add on are flashlight and laser.
Flash light on your pistol gives a bad guy an aim point directly in front of your face. Call me old school, but I would rather hold my flash light in my off hand, out away from my body.
I just don't have the inclination to put a laser on my weapon. (Although I will concede the point that putting the laser on the mark might, in some rare instances, cause a bad guy to back down.)
I would probably change my mind about the laser if I were LE, but I still have trained to hold the flash light in my off hand and I'm comfortable with that.