I personally bought a pair for self belay purposes in a top rope solo scenario, and so far I'm happy with them. They feed easily and catch instantly if set up correctly. They can be tricky to disengage (sometimes even when unweighted) and they don't like to stay unlocked during a rappel (although I can't complain about this too much... vs. the other way around). I end up having to take them off completely to descend and install them again to start another lap. If oriented correctly, they pose no damage to a rope and I feel secure. I haven't used them as a rescue pulley yet, but I'm sure they'd be awesome in a progress capture haul setup. For general purpose, I can see the catch not staying unlocked and providing some annoyance. But otherwise, they're great! I've started sneaking them on my MP routes. They're light enough and small enough to be negligible.