The app is a single-tasker -- it is a bulk file renamer, much like Dare to be Creative's Renamer (US$29). Like its more expensive competitor, you can rename any batch of files, not just photos. While I don't think that the user interface for Photo A.K.A. is as well-designed as Renamer, the former application does have several features that can't be found in the latter.
For example, Photo A.K.A. can rename files, stuff them into an archive file, and then email the information to someone. There's also a handy built-in function to directly upload your renamed photos to Flickr or Picasa.
But wait, there's more! Photo A.K.A. can also burn your renamed files to a CD or DVD, or create a disk image file containing the files. It can also do batch resizing of photo files, display the renamed images as a slide show, and even batch print the files. Finally, there's a sandbox mode for trying your renaming scheme without actually renaming the files.
While Photo A.K.A. might not fulfill all of your file renaming requirements, it is free, and it has many features you may find useful.