This is a superior belay carabiner, in that it keeps your belay loop locked in one end even when you get slack in your system, pretty much guaranteeing that when it loads up, it does so on its major axis every time. It does require that you actually put your belay loop inside the internal gate, of course- I haven't seen what would happen if I didn't, but I expect that the worst-case scenario would be that the internal gate would bend or break. The internal gate does make this a fairly specialized piece of gear (perhaps not ideal as, say, a master-point with multiple cordolette strands to stuff inside the minor gate) but for belaying or your personal anchor, it's a superior piece of gear.

It's my locker of choice to mate up with my gri-gri for this reason: it stays put, while similar lockers (ones without a retention gate) rotate a bit as you give and take slack- occasionally resulting in gate-loading the belay locker with your buddy (or in my case, my wife) on the other end of that rope.

The locking gate has a 3-way release- you slide the collar down, then rotate the collar, then open the gate- this sounds cumbersome, but it becomes a quick one-handed motion very easily.

I've had it for one season now after using normal carabiners for about 6 years. It is a great belay carabiner to use with an ATC. I thought the inner clip was a gimmic, but I really like it. It keeps the carabiner from rotating on your belay loop when the rope is slacked, and normal carabiners spin very often. It's nice to know it's always on its strong axis and the darn gate doesn't get annoyingly snagged on the belay loop when loaded. I don't like fussing with a belay. It's one of those things you wouldn't even notice till you get this. Make sure you clip the inner clip over your belay loop because unclipped and loaded feels awkward. The spring gate is especially nice for the belay carabiner.

It's not so nice to clip into burly toprope anchor points since the clip side is so narrow, but I believe it was primarly designed for belay, and it excels at that.