I have this system on my mossy 590 and I like it although it has shortcomings.
Pro:
Great Value for under $100.
The light is VERY bright and the batteries last a long time.
The mount system is flexible and easy to use.
The pressure sensitive switch is well made and has stood up to hard use.
Con:
I had to loc-tite the mounting screws to keep them tight, they would shake loose after 25 rounds. No problem after loc tite.
I didnt want to glue the pressure switch to my foregrip so I used heavy duty velcro. It tends to come loose over time and if I leave the weapon un- checked for 6+ months, it will usually have detached itself, it re-attaches fast but really should be glued in place with a good epoxy. In the (doubtful) event that I ever sell this shotgun, I would keep the light system so I didnt want it permanently mounted.
I would buy the same system again if I was setting up another HD shotgun. Its a good price performer and I have been pleased with it overall.
Blatant "look at my shotgun" pics attached.