They've been discussed here before - try the search function, maybe?
In short, the design leaves some things to be desired - the single action bar tends to break, and the stock tends to break off where the stock bolt screws into the cast aluminum trigger plate. It's hard to field strip and clean the action and on most variations the barrel is fixed, so it doesn't take down. Spare parts are difficult to impossible to find and there are few accessories for them.
They were inexpensive shotguns to begin with, and some of them have held up well and their owners are happy - but many have broken down.