I love PicMonkey. Love it love it. I was very fond of Picnik, which is closing in a couple of days -- PicMonkey was started by a few of the Picnik engineers. It has the same cool factor, but it's a little different.

Why is this great? Because it's a satisfying and easy way to manipulate your photos. 

I had opened another, similar, app today (which I won't name) and it looked... hard. Hard to learn and hard to use. I closed it. Fast.

Consumers want easy and they want fun. Products that provide this do well -- those that don't, dont.