I've been a few times, and it's quite good fun! I've never really got into it, more gone along with other people.
There is usually tat in the containers. Like toys out of crackers! You take something and leave something. Write in the little log. Then log online you've done that one.
The best finds are the bugs (I think they're called??). They have a proper log, start place and often a destination
so, say you wanted one to travel around the world, you can set it off, then track it as it travels to far off places. Or if you find one, you can help it along its journey.
It's just like a grown up treasure hunt.
And make sure the muggles don't see you!!!!!!!
And for those who don't like the outdoors, there's tons hidden in cities too