C-Mores are fast - used widely in action sports on pistols and shotguns. I see them in USPSA and 3gun, and have for the past 20+ years. I bought several with the FN offer years ago (they were offered with several of their shotguns, although I never mounted one on a shotgun). I use them on pistol caliber stuff, and, as noted, they have a huge FOV, little to obstruct the target, and just plain work.
Down side is primarily the power side of things. They generally run off of 1/3N batteries, they don't have auto-off or motion sensor features, and the battery life isn't remarkable. In addition, the adjustments are not click adjustable - you have to guess and iterate on the adjustments to get it zeroed. That's fine for shotguns and pistols used up close and fast, but more of a pain if trying to absolutely zero a rifle for precise shots.
Also, there are several options for them: body of plastic or aluminum, size and interface for dot (dot sizes are changeable - just takes another module of the proper interface and you can go from a 4MOA to an 8MOA dot, for example), adjustment switch options (smooth rheostat or click adjustable), built in pic rail base or not, built in A2 rear sight for cowitnessing or not, etc.
All that said, if you're still interested, PM me as I probably still have at least one ARW-4 NIB. That's the aluminum body, 4MOA reticle, click adjustable power control, and built in pic rail mount. Those were the top of the line models when I got them, and what were offered as an option with the FN shotguns a number of years ago, so I'm guessing is the model you used and liked.