I've used this technique on rock many times with 8.5mm ropes. I have found it to work well. Any fall was immediately stopped with the self locking action of the reverso. I have not tried it on ice climbs though. In this case, it does seem logical that a wet skinny rope will provide less friction. Guess you just have to add additional friction with brake hand or other method. As far as the rope being cut over a sharp edge, I find this situation only to be a serious threat to the leader, who may fall over a sharp edge, but since the leader always leads with two lines, that's not as much a problem. I suppose it is possible to severe a single line while TR'ing, but it would probably require the follower to take a long swinging fall over a sharp edge. Of course, a fall of this type could be avoided by the leader protecting the route in manner to avoid the second from taking a pendiluim swing fall. The biggest problem I have seen with the reverso, is lowering someone who is hanging on the rope. It can be done, but not easily. I only use this technique on easier ground to save time for a three climbers.