For anyone interested in image processing, this post on the Wolfram blog might be interesting. I think it's pretty neat, and it surely could simplify rapid testing of custom filters and image processing functions. It's often a pain to spend a lot of time coding up what you thought might be interesting only to learn that it wasn't so useful. And, I agree with what they say about Photoshop scripts... it's just not as nice as interfacing with a real API.
Of course, everything shown in that post can be done with your own image processing libraries and your own front-end, but if it's easy to do with what they've got, why not use it. I'd like to play with the new Mathematica some time, but unfortunately, that time isn't available now.