I've been kinda going nuts with it:
AND you can even take photos you already have and use their filters too. I took a hair show photo form last year where the overheard fluorescent light killed the photo, making it unusable, and added a simple filter that takes off the strong highlights and gives a sepia feel to it. Now I look like a vintage movie star!
You can also have it connect to Facebook, Twitter, Foursquare, etc or you can keep your photos private.
It is a ton of fun!