jef1002932822-0wrote a review of Mammut Smart Belay Device on August 19, 2013
Familiarity: I've used it several times
I have the 2 rope and single rope versions of the Mammut Smart Belay, and I love them. I've been using various versions of the ATC for many years, and the smart belay works almost identical to an ATC - so all my muscle memory already knows how to use it safely. (unlike a grigri which requires different muscle memory than an ATC)
In the gym, I'm more confident knowing that my belayer will always catch my fall (because the device will catch automatically). I also find it easier and faster to feed rope to a lead climber than with ATC (or ATC guide). And, it's easier to control the descent (for lowering or rappelling) with less friction on my hand due to the "handle" taking much of the friction.
Better braking, auto catching, easier feeding, light, inexpensive. I can't think of anything wrong with it. I recommend this as a replacement for the ATC for sport and trad use.