We think the new Mega Jul is one of the best belay devices on the market today - it's more versatile than any we've come across in this price range.
Firstly, it can obviously be used as a standard ATC style device with single or half ropes (the recommended rope diameter is a whopping 7.8mm-10.5mm), and can be used for bringing up one or two seconds much like a Petzl Reverso or ATC Guide.
What sets the Mega Jul apart is that it assists the belayer in the event of a leader fall, much like the popular Petzl GriGri, but without any moving parts. To lower the climber once the device has locked, you simply release it with your thumb. allowing you to keep both hands on the dead rope while lowering. Ideal! This might take a bit of getting used to to lower smoothly, but it's much simpler than any other auto-blocking device we've used.