I just got my Benelli M4 near the beginning of August and have already modded it somewhat and plan to add a few final touches.
It has the Mesa Tactical OD Green Stock w Limbsaver pad and Cheek Riser (Cheek Riser currently not in use) / FFT OD Green Forend / FFT 3/4" Ti Charging Handle (not shown since I just got it)
I have shot ~200 rounds so far of a combination of 7 1/2 shot, #4 Buck, #4 Magnum Buck, and 00 Buck. No issues to speak of.
I plan on a carriercomp full mag tube order this week, sling, US follower and Hammer and maybe bigger bolt release.