I’ve only recently been using Foursquare mainly because I wanted to keep my own personal log of what I’ve been doing or where I’ve been going every day. It’s not very easy to get an overview of it with the app, so using an IFTTT recipe, I managed to sync it with one of my Google Calendars and viola! An instant overview of everything!
Seriously, it’s just so awesome (at least for me). I don’t really use Foursquare to let all my friends know where I am; the bigger motivation is this log and there’s so many what-if-I-need-this-info scenarios in my head that makes this useful.
As a side-note, since I log all the restaurants I go to, I end up getting an idea of how bad (or good) my diet is for that month/week. :P