I too have the M&P 9L pc have had it a couple years now and it's by far my favorite! I have never touched the sights..never needed to. Love the trigger, very smooth. As far as the barrel..well it's a give and take kinda thing. Yes after a couple mags I have to give the front sight a wet thumb wipe and back in business. I really haven't had a problem with cleaning my barrel. I soak it in hoppes while I go thru the rest of the gun...then I use a brass wire brush and it gets the job done.