UPDATE: I’ve not used Apple’s app at all…other than in an initial trial. I do much of my photo editing for online posts in the ancient PaintShop Pro and on the iPad with SnapSeed.
I am so glad I didn’t waste $10 on Photoshop Touch now that Apple’s own iPhoto is available for iPad (and other iOS devices running 5.1). As you’d expect it uses simple gestures to quickly sort through photos and find your best snaps. It has a powerful set of Multi-Touch tools to control saturation and exposure, to crop, straighten, and otherwise retouch images.
You can also add various effects with just a tap or use fingertip brushes to apply adjustments exactly where you want them.
Of course, the app also has Facebook, Flickr, and Twitter integration and you can stream photos and slideshows to an Apple TV with AirPlay or use iCloud to publish photo journals to the web or share with friends and family.
The new version of iOS also allows you to delete photos from your Photo Stream (whether you have iPhoto or not)
iPhoto for iPhone 4, iPhone 4S, iPad 2 Wi-Fi and iPad 2 Wi-Fi + 3G.