I just installed one a few days ago. I'd have to rate the quality of the device very high. It's certainly quite strong and beefy, has a high quality lock on it, and the device is completely padded and rubberized to protect your gun (didn't really matter with my beat up Mossberg 500).
The mounting hardware was more than sufficient. The large lock portion is secured with three very large screws that I was hard-pressed to get screwed all the way into the studs (soap is your friend here). Thankfully the #3 philips screws provided seem much less prone to "cam-out" than #2s. Once you screw the lock portion into a stud and screw in the muzzle hook, the gun is secured by slipping the barrel around the muzzle hook, and then placing the open action over a small hook in the lock-box portion. Based on the mounting hardware provided, it would take a very significant amount of force to get it off the wall. But the way I look it it, that wouldn't even be that big of a deal due to the way the gun is secured in the mount.
Again, a small padded hook in the box portion goes into the open action of the shotgun. In this way, it is impossible to close the action when the loc-box is locked. So even if someone did manage to pry the loc-box off the wall (an eventuality I'd call near impossible), the gun would still be totally inoperable. It's every bit as safe as a safe in the "child-proof" sense and the "keeping-burglar-from-using-it-on-me" sense. If someone was looking to flat-out steal your shotgun, even if an extremely determined burglar was able to tear the thing off the wall, he would then need to go somewhere and spend a few hours cutting the lock-box off the gun before it would be operable. I don't see this as a particularly large risk with low price and wide availability of home defense shotguns.
Another nice thing is that if you want to keep the gun in a higher state of readiness for some period of time, you can unlock the loc-box, swing the little door open, and the shotgun is supported in such a way that it will not fall out. I have the loc-box near my bed, and am able to keep it unlocked and quickly accessible during the night, and then lock it back up when I'm not there.
As I said above, the loc-box does require you to store the shotgun with the action open, but the hook portion of the lock unit is small enough that I can (with my 500 anway) keep the shotgun in the lock with a full magazine and one round floating around inside the open action. In this way, should I need to use the gun all I have to do is close the action and I'll 5+1 rounds ready to go.
I was able to get mine ever so slightly cheaper at
www.outdoorsuperstore.com
Overall I'm very pleased with it; it's an excellent value.