Unlike most reviewers, I was going from a B-52 to the Guide rather than from the Reverso. The B-52 is the smoothest device I've ever tried for rappelling, belaying and lowering. It works great in autoblock mode for fat ropes, okay for doubles and probably not recommended for twins.

The ATC-Guide works fine for belaying and rappelling on fat ropes in low friction mode, although it is not nearly as smooth as the B-52. Naturally, with the grooves it can provide more than enough friction for skinny ropes.

When I went to try it in Guide or Autoblock mode with a 10.5 mm rope, the friction bringing in rope was so bad I went back to the Munter Hitch. It's okay on 8.6 mm half ropes but you can forget it on fat ropes.

I read a review that said two biners make for much less friction in Guide mode for fat ropes. I have yet to try this. Hopefully it will do the trick.

Of the three locking modes, I prefer the Lift and Twist one over the Ball Lock because it can be done more easily with gloved hands. Non-self-locking types can come unlocked, or one can forget to lock them.

The keynose feature is really nice when dealing with 5.5 mm cordellettes, as it doesn't hang up on them.