I have one and I like it. I also just bought an 870 but I haven't got a chance to fire that yet, so I can't compare the two. Here's what I like about the Defender:
1.) It's fast. I can pump and fire that thing fast enough to keep a can moving without the can stopping or slowing.
2.) It's easy to take apart and clean.
3.) It's light.
4.) The mag tube is right on.
Here's what I don't like:
1.) The bolt opens pretty easy. If it's just cracked a hair and you go to load a shell into the magazine for a refresh, the shell will bind and get stuck. I don't like that. That's the price you pay for the speed of the pump on this weapon.
All in all, I like mine. Now that I have my 870, I still won't sell my Defender. It's a good shotgun. No, don't try and make a hunting gun out of it. That's not what it was made for. But it is a helluva fun gun, it's fast as greased lightning, and it would live up to it's name if it had to with aces high.