I am always on the prowl for something a little different in a photo editor, and Truefilm (US$0.99) meets the requirements with a comprehensive suite of tools at a low price. The emphasis in this app is on making changes quickly and having a complete ability to go back and try things again.
There are the usual adjustments for photos, but they go deeper than a lot of editors. You can play with color temperature and balance, there is an effective clarity tool for sharpening, selective blur and a patch tool for removing blemishes. The latter isn't something you usually see in an iOS editor. Crop tools are one tap away in a variety of aspect ratios and you can create your own cropping shapes.
Truefilm provides a wide variety of frames and some useful filters that are subtle rather than garish. There are also some black and white transformations. Text can be added with various colors and levels of transparency.
Truefilm for iOS
I think one of the best thought-out tools is the history view. It's a bit like Apple's Cover Flow; you see a series of stacked images that represent each saved edit to your image. You can roll the history back and forth, then tap on the edit you want to preserve. This is far more useful than endless undos.
No app is perfect, and that's the case with Truefilm. I'd like to see curves added, a tool that digital photo editors use all the time. Also, I'd like to see some more tools for blurring. The way the app works now, you use the clarity tool and slide it to negative numbers, but I'd prefer a dedicated global blurring tool that supports gaussian, lens blur and other forms of modifying the image. Truefilm does have a useful smoothing tool, but I think that is more useful for portraits.
All in all, Truefilm packs some excellent tools in a $0.99 app. It's not trying to offer 200 filters that you will never use; instead, it offers about 20 that are really useful. The face retouching tools are something I don't see on a lot of general editing apps, and the History View is unique and useful. I like Truefilm and the price is reasonable. I'm adding it to my suite of editing tools.
Truefilm is not a universal app, but will work scaled up on an iPad. It requires iOS 7 or later, and it ran smoothly in iOS 8 beta 4 during my testing. I don't expect it to have any issues with Truefilm when the iOS upgrade hits this fall.