Seems to me that the magazine disconnector in my old M39 would affect the trigger pull, although I don't remember for sure. I took mine out to match my PPK/S when I was carrying those two, but that was a long time ago, and when somebody suggested that I put the thing back, I did.... (Very simply, it's not a good idea to tamper with a manufacturer-supplied safety device, as silly as this one is.) Both range guns now.... (Well, in so far as a PPK/S can be

.)
About the "can't be seen by a metal detector" post.... Huh? It's not a Glock

, and there's enough steel in mine to get smaller weapons to orbit around it

.... (Well, you get the idea.)
I wear a Streamlight Nano around my neck, and the last time through the body scanner at PIT, forgot to remove it. They spotted it, although didn't know what it was until I showed it to the TSA guy at the end of the line.
Just IMHO, but the full size M&P's make a fine replacement for an Officer's "service revolver" - like S&W's Model 10, and the Compacts are fine for soft clothes or concealed carry while having a lot of advantages over the old J-Frame guns (like the Chief's Special). In addition, the .40S&W, while not all that impressive, is a bit of a plus v.s. the .38Spl (and .357 Magnum) without being all that hard to get used to, even in the Compact guns.
Don't forget that these things are stamped out like, well, stamps, and anything can happen. The overall design allows for fairly easy adjustment or repair should something go really wrong, and generally they work, even if not quite right. (I'm a little concerned about the trigger spring issues, but the Apex RAM kit can help there.)
Regards,