I like the inertia system and have the poor man's M1 (Benelli 1201FP) for home defense and a Benelli M1 with wood furniture for a field gun. Both stay amazingly clean compared to a gas operated shotgun. Both guns have been excellent and I have no plans to add a gas operated shotgun. They do kick a little harder, but I am use to it.
I always heard that they were finicky when adding weight like a light, but I don't have any experience with that. Today, lights are getting very light and small compared to when these guns were manufactured so you probably could find a small light that wouldn't effect it.
http://www.amazon.com/Lumens-Ultra-C...4T7SW8XRQDRAVR