What's the purpose? Where do I start?.....
As an advertising/lifestyle/fashion photographer (
http://chrisborgman.com) there are MANY times when I need to see a flipped/mirrored (flipped horz.) image for myself or to show a client during consultation. This is a matter of design while editing. Being able to view an imaged flippled while making selections for a series of photos such as for website, portfolio, promotional cards, books, magazine layouts and covers, newspaper layouts and covers, etc... would be a great help. I would also use the feature while selectiong elements for compositing in Photoshop. Being able to see 2 images side by side (one background, one subject) and then being able to flip it to see if it works better W/O going into PS every time would be a BIG time saver.
I just thought if you can crop an image why can't you flip it. I would love to see this in PM but I understand it's place in the workflow. You put in all the features people want and then you get Aperture/Lightroom that's slow and doesn't run well on older laptops. I just thought that these programs offer everything but don't do a simple task as flip image. Maybe PM can be the first to offer it. The others will follow....
Chris