Lots of folks have been waiting since SHOT last year for Magpul to release their Mossberg shotgun furniture and it's finally started shipping out. I snagged a set and here's what I've found so far:
-Good texturing on the grip.
-LOP is user adjustable between about 12.5'' and 14.5'' (my measurements, it may be slightly different officially).
-There are different height combs available for use with optics
-You can put QD sling attachment points on either side of the stock.
-The grip angle puts your thumb in a great position to work the safety.
-The trigger group doesn't drop out for disassembly as it should with it installed. Easy fix but it's worth pointing out.
-Some folks think it looks ugly but it's grown on me over the past year since I've had it on my 870s.
-Handstops in the front and back of forend provide a good grip to run the action hard.
-3 slots on the left, bottom, and right provide a lot of options for mounting accessories on the forend as the user requires.
-Not so much a con but with all the Mossberg 500 models floating around out there it may not fit your shotgun (see the video for examples). Most will work however.
All in all, for around $140 MSRP the addition of the stock and forend are an excellent upgrade to your fighting shotgun in my opinion. I'd certainly buy them again. Here's a video with some shooting, a discussion of the pros/cons/features of the products, and what I think of them overall: