My wife bought me one for Christmas and these little gizmos are wonderful! The loop feature has allowed me to figure out passages I would have taken weeks to come close to before.
I've been pulling info off the web about modes, scales etc and this box is helping me put it all together by reinforcing the academic stuff with on-the-fretboard exercises. New doors are opening as I have a much better idea of where I am on the board and where I can go in the context of the tune.
They do eat batteries though so I'm picking up an adapter today.
TT