This is an interesting new site. From what I can tell it doesn't add much value to me right now but as I obtain more friends, network externalities should make my experience more enjoyable. Emotionally, I really like the site and I like checking into places and hopefully I will become the mayor of a place some day but logically, I don't see any value add and I feel like I should not like the site as much as I do.
The concept is that the user can check into places, which will let his friends know where he is. If the friends are in the area, they can meet up with you. The downside is that this could be a bit stalkerish if someone keeps following the user.