In reply to Will: To satisfy my curiosity, I went out and bought myself a reverso. Any excuse to get a new toy! I paid the smae for it as I did for my ATC, so no difference there. I then took it down to a local quarry to try it out.
First impressions are that it is a smoother ab device than my ATC (which I also had with me, and which I also abbed on for comparison), and the self-locking mode does indeed work as advertised, including for self-belay.
I also discovered that it is quite easy to switch from self-belay/ascent mode to abseil, by clipping the "locking" krab back in to the harness ab loop and then unclipping the other krab. Obviously you need to keep control of the braking rope while you do this.
Next test will be out with partner using it as a belay device on both single and double ropes.
I don't completely agree with all of the issues which Rob S raised:
1. It's true that you can't give slack when using it self-locking mode, but that is mentioned in the instruction leaflet and anyway you don't have to use it that way if you don't want to.
2. I don't think the "thin sharp edge" is any more so than on my ATC. At least, a fingertip comparison of the two doesn't indicate any detectable difference.
3. The second metal loop does make it a more complex design than an ATC. However, I think it would be extremely difficult to rig it using the wrong loop, and even if you managed to do that it would be so obviously wrong that anyone would have to be pretty dumb to start climbing belayed like that.
I'd agree with Simon, that it does what it is designed to do very well. It's probably not the best device to give to a beginner, but then again I don't think it would take much teaching and experience to be unlikely to kill anyone with it. Anyone who doesn't need the additional features and capabilities it has over an ATC or sticht plate can stick to what they know. The fact that it can also do some of the same things as some other bits of kit does not, to me, mean that I can leave those bits of kit at home. It just means that I have a fallback if I lose or break any of those other bits of kit.