In reply to davefount:
I must admit to being disappointed with my Reverso in 'guide' mode for this very reason. I've found myself as pumped belaying as I have been whilst climbing the pitch. I've got the Reverso to replace my old NewAlp Magic plate, which I've had since it first came out and which was the first of this type of device. With the Magic Plate it is EASY to run the ropes through with any brake krab, but at the same time is mechanically just as secure as the Reverso. Unfortunately it doesn't have the other functions that a Reverso has, and to abseil you need to carry another device as well.
I wonder whether it's JUST the choice of krab that makes the Reverso hard to use. I suspect it's partly that, but also the very aggressive V-grooves that the rope runs through. I'm hoping the with time the grooves will wear and the handling will become more like the Magic Plate. Following the above posts, I'm also going to try the largest diameter krab I can find!