On the other hand, so long as the grooves aren't too developed, they can reduce any tendency to put the guitar out of tune when you capo up. Especially on the bass strings - Rick Fielding recommended cutting a groove for teh bass E at least, but I've found that the Keyer seems to do that for you itself, if you leave it on the strings.

I think it's probably a good idea to leave the capo on the strings when you buy it, and then, once the grooves are settled in, start removing it from the fretboard, when you aren't using it.