If you like the savings from check ins, have a look at our connected app, GeoPerks (http://4sq.com/Q8uIW3). You get replies to checkins at venues where you have membership discounts and rewards (e.g. AAA, museum memberships, student discounts, etc.).
And, of course, I still like earning new badges.
edit for additional note:
If you have friends that use it heavily while on tours it is fun to track their travels. Follow an entire band or tv crew on tour and get anecdotes from different personalities live updated as they travel - it's like a real reality show in small doses.