Photoshop Mix has been available as a free app from Adobe since June of 2014. It's not only a fun tool to play with, but it solves some important, sophisticated imaging needs without having to jump right into Photoshop itself.
Below are a few examples of how I've found Photoshop Mix useful.
UPDATE: Photoshop Mix from Adobe is now considered a legacy mobile app and may not be supported by current or future mobile OS’s. Everything that PS Mix can do, is possible to do in Photoshop for the iPad, Photoshop Express and to some extent Adobe Express.
A recent iPhone shot, before and after processing in Photoshop Mix. Becuse you can only add ONE look to an open image at a time in PS MIx, I've established a workflow where I add the effect, save the file as a new image, reopen the file and process with addtional looks. I keep going until I'm happy. For example, this image took a total of four renditions. You can learn a bit more by checking out my Work in Progress for the image below. I'm finding that I really like working with Selective looks, whee, using my finger, I paint on the effect in the desired areas.
I plan to experiment more with Photoshop Mix, working on Collage style imagery next. I hope you've found these examples helpful and that they inspire you to try things out in Photoshop Mix, too. The app is currently available for the iPad and iPhone.