I've been using Petzl's Reversos since they came out in the early 2000s. Works very well with thin double/half ropes as well as single ropes, thick or thin. In the so-called "reverso" mode, belaying two seconds simultaneously is very easy. When belaying the second it is autolocking. When rappelling it may produce a bit too much friction but it all depends on the rope you're using. Packs a lot of value in a reliable, nice looking, low weight piece of hardware. Highly recommended.
This review was written in the old system and had content requirements that are different than reviews written today.