They are great for running bolts into waterbottle cages, oddly placed xtracycle bolts, oddly placed rack bolts and fender doodads.... then get in there with the tool at the proper angle for the last turns of tightening and the first turns of loosening.

I've never rounded anything off. (...knocking on wood)ar

People should indeed be well aware that they are more likely to round off a bolt. But the convenience is worth it. Try them sometime.