I've done a few local ones with 'er indoors - it's a good excuse for a country walk, maybe find a few places that you sort-of-knew-were-there-but-not-really.
It all seemed a bit, well, sterile - rather solitary, overcomplicated maybe.
I've got a lot of the local ones loaded as POIs on my Garmin 605, but without the clues, printed out, and remembered to be taken, then the POIs are next to useless - I passed one on my ride home through Charnwood Forest, but I couldn't go looking for it, as I didn't have the cheat sheet with me.
And to go back to a point a previous poster made - Audax and Geocaching = a synergy, yes definately, and I'm surprised this hasn't been explored, this synergy could get me back into both Audaxing, and Geocaching!