It's my new addiction.
I guess the best way to describe it would be twitter meets flickr.
You can snap a picture, choose a filter (or not), and the image is shared with your friends.
There's even the option to post directly to twitter, fb, flickr, etc...
Your friends can like and post comments.
It's pretty cool for the photo enthusiast.
The camera on the iPhone 4S is pretty sweet too, so pictures turn out pretty good.
The girlfriend uses, and loves, Instagram.
I currently have the original iPhone (one that my cousin got when it first launched) and once I upgrade the OS on my Macbook I will update iTunes and jailbreak the girlfriends iPhone 3G and download this app.
@andydel on instagram but I prefer Pixlromatic and it's filters for in camera editing/customizing. Pixlr doesn't have the built in sharing features of insta but has it beat in the filter department imo.
Has anyone tried out Filmlab yet? It's a GREAT concept but I can't get it to run right on my 4 with iOS 5.1. It's workflow is pretty clunky too, which is a shame