I have had one for several years and my round count is in the 4-digit range. I use it for 3-gun, training, and have carried it in the trunk of the squad car a little bit. So far, I have never had a malfunction. This is not a surprise, because Benelli makes guns that don't die. I've had a Benelli SBE for 11 years with a round count in the high 4-digit range and that has been 100% reliable as well. Several of my family members have Benellis (Montefeltros and M2s mainly), and to date, none of them have ever had a malfunction.
The M4 uses a different recoil system with the ARGO (auto regulating gas operated) short stroke dual piston operating system, as opposed to their conventional inertia operating system. This allows it to shoot light loads that other autos have difficulty with. The problem with cycling less-lethal is not abnormal. Such is why dedicated less-lethal shotguns are relegated to pump-action or single-shot only.
The shotgun is front-heavy, but that's pretty normal for a tactical shotgun. The reliability is phenomenal, as previously pointed out. The recoil will be more than a typical gas-operated shotgun, but less than a pump gun. It's a 12ga.- what can you say. None of them feel like a tickle fight when you shoot them.
Standard configuration is the 11707 model with the pistol grip and fixed stock. It works very well and is all you would need. However, if you decide that you want the Benelli tactical retractable stock, check out Gunbroker.com or another online sight and you can find them for sale for $600-1k. Some gun shops have also sold these stocks to the public in the past. If you find a shop that is selling them, it's up to you whether or not you want to buy it. I've heard of people buying them for up to $1k there too. Just know that the stock itself only costs $150 and is not supposed to be sold to the public. The amount of red tape I had to go through to get mine legitimately was nuts, but well worth it.
The magazine capacity is only 4rds (or 5rds, ammo dependent), but that's because the magazine tube is the same that's used for the 14" barreled Entry variant. If you get a mag extension, you will up the magazine capacity to 7rds.
I would recommend also getting a Mesa Tactical rail and side saddle ammo carrier. These are things that make life much more convenient.
I would also recommend looking into other custom parts for options. The SureFire M80 picatinny forend, the Meprolight tritium ghost ring replacement sights, GG&G extended bolt knob and bolt release button.
Good place for accessories:
http://www.tacticalshotgunner.com/benelli-c-66.html?osCsid=be629df7ef1987a7662a268ac552797f