I have the Defender for a full size M&P. Only use it for OWB though.
Also have one of their single mag carriers for double stack pistol and an AR.
No issues with any of it and I run my gear pretty hard and regularly. To be honest, the only reason I bought it is because my LGS carries it and I try to give them as much business as I can. Also it is cheaper at my LGS than direct from their website. It's comparable to most of the big kydex names in the game. The Defender is very similar in quality/comfort to my Bladetech Eclipse. If I was going to order online however I would stick with Raven or Bravo (not really because I think they are better, they are just more "proven" I suppose or maybe I'm being a brand snob idk).
Short version. I have a Defender. It works well.