Who has participated in Geocaching?

Geocaching is an adventure game for GPS users. The basic idea is to have individuals and organizations set up caches all over the world and share the locations of these caches on the internet. GPS users can then use the location coordinates to find the caches. Once found, a cache may provide the visitor with a wide variety of rewards. All the visitor is asked to do is if they get something they should try to leave something for the cache.
Link: http://www.geocaching.com/

So now as you know what is it and that it can be experienced but not eaten, what is your opinion on idea like this one, will you participate, if you have already been through this one, what was yours like?