I have a collection of belay devices and have tried them all. This is the only one I use for sport or TR. Much easier and safer to belay leader than gri gri. Excellent for belaying someone working a difficult route. It loves catching falls over and over. Simple to rig and easy on ropes. Great on skinnier ropes (9.1-10)
Slightly heaver than a gri gri, but if you are gonna haul a gri gri, this is worth its extra weight. It also takes a little practice to lower/rap. I believe it is rated 9.1-10.5mm, but anything over a 10.1 is a little bit tougher to feed lead.
I wouldn't use this for trad, unless you are really careful. I have 6 different "auto-locking" belay devices and 4 of them sit in a box in my climbing room (the wife has the gri gri on her harness). As far as they go, this is the way to go!