One my uses for the capo is to switch between - singing and picking a song.
For example - I enjoy singing Dark Hallow in the Key of C - however FM had given us the tune in the key of D for picking. So when I first started the Wednesday night classes 2 yrs ago - I had a problem with trying to sing it in D - which is a bit high for me. As a result I had learned to pick it in C - and capo up 1 tone allowing me to pick the tune-in class -in the key of D but chording in C. When I'm outside of class with friends - I skip the capo -& so I can sing it (and pick the breaks) in the key of C only.

Works for me!

I play in my church's worship band. Bless their heart, the worship leader tolerates me. We get tunes from a familiar artist in a weird key, like A#/Bb. I'm not gonna learn all those barre chords for an enharmonic key. No sirree. I wanna use my capo, and reverse engineer. I study this artist, and i know he always plays Gmaj. shapes, and look at that, he's capo'ed 3! A#! Bada Bing! No wonder the capo is our friend. Just reverse engineer the tune's chords so they sound like the enharmonic key, while playing familiar shapes with my capo...and a smile....

Ponhook, that's another reason the capo is your friend. I'm thinking it could be better than a mere friend sometimes. It's time the poor little spring loaded chap got more credo....After all, they cost enough! The Kyser i use cost $20 @ a local guitar shoppe....but hey, if you wanna play, you hafta pay...