I've been playing it and so is my wife (and son when his new sim card turns up!) We went out for a meal with friends on Sunday evening, and left the house early so we could go for a walk in a nearby park beforehand (as it's packed with Pokestops!), something which we wouldn't normally do. The park was a lot fuller than it would normally be, so it seems it's getting more people out walking, which can only be a good thing.
It seems that the locations of Pokestops and gyms are taken from the Ingress game, so you can check out likely locations on the Ingress web site. Apparently trading and battles with friends etc. is all on Niantic's plan going forward, hopefully after they've fixed the problems with the servers and Pokemon tracking.