I've been using this biner for belaying for the past couple seasons and I must say, this thing is DURABLE. I've had a fairly insignificant amount of wear from the rope, even with moderate-heavy use in the past 2 years.
It's huge so the belay loop on my harness feels as if it's angel hair pasta when I'm all hooked up. I have the auto-locking (double action) version with the red gate, and I can open it really easily with just one hand.
This is such an amazing belay biner and I will surely buy another one once mine is worn out.