I've never come across this pokemon business before, but I downloaded the app yesterday and went out for a couple of hours yesterday evening.
It's a really interesting concept in some ways, and I was amazed at the number of people playing it already, there must have been about 15-20 others last night, and quite a broad spectrum of people.
I think it's a great idea, in that it will encourage people to get outside, and Im pretty sure it will really take off in the UK when officially released.
By heading to a couple of the Poke Stops, I actually found out a few bits of info about my local town that I didn't know too.