The belay device operates almost identically to my Petzl Reverso. Other than the shape, I don't feel a difference. But just like others here, I also encountered a torn plastic keeper loop after a normal rappel. Mammut's customer service told me it was user error, and I was racking my brain trying to figure out what I might have done differently on that rap, so it's good to see some reassurance that it isn't me! They did still offer to replace the device, however, and were quick with their reply.
Purchased this rope in May, for sport climbing in Boulder Canyon. It's now October and there's significant fraying in several places. We climb maybe once a week, so I'd guess about 16-20 days so far, but switch back and forth with another rope, a BlueWater rope, that's two years older and shows none of the same wear. I'm actually going to have to retire this rope in one season, and I've never had to do that before. Haven't climbed any harder or sharper (generally rap down, and always keep an eye on sharp edges). I babied this rope, but it didn't help. No more Mammut ropes for me. I recommend you look elsewhere!