I've heard about it for over 5 years and tried it a couple of times. It's alright... It's really one of those things where you have to be fortunate to live in an area where it's popular and you figure out where the "good ones" are.
There are some geocaches that are legendary. Unfortunately, they eventually get ransacked by a degenerate who wants to spoil the fun. But if you really get into it, you can make some interesting friends and make some intriguing finds. I've been meaning to give it a go once more, but other things have taken priority.