Scanner Pro (iTunes link) from Readdle transforms your iPhone into a portable PDF scanner. For US$6.99, you can combine pictures (chosen from your iPhone photo library, or taken using your iPhone's built-in camera) into a PDF document that you can e-mail or upload via WebDAV.
That's a really useful concept, and if Readdle had delivered a user interface as strong and usable as its underlying idea, I'd recommend Scanner Pro as a must buy. Unfortunately, the application desperately needs the tender loving care of a user interface design expert. [For a different -- and much simpler -- UI approach to the same kind of task, you might check out the $2.99 JotNot.]
The UI is cluttered and confusing. You're forced into unnecessary screens by a poorly designed work flow. Here's an example; once you scan a new page, the interface asks you to either go back or to process the image.
Tapping the Process button enters a processing screen, where you can then click an Adjust button. This finally reveals a pair of sliders for adjusting the brightness and contrast settings for grayscale and color. The screen shot at the top of this post shows the Adjust screen.
The sliders do not provide any live feedback. You can adjust them all the way down and all the way up (the shot was snapped with the slider set to 100% Brightness) without any change to the image you're seeing. The enhancement gets applied after you click Apply. At the same time, the sliders disappear. Want to make a few tiny changes? You need to Adjust/Slide/Apply for each adjustment. That's bad design.
As you can also see in that picture, the (hard-to-see) undo and redo options appear tied to the grayscale and color choices, but in fact they are not. That's bad design. The fonts used and the button choices throughout the application are pretty ugly as well. Consider the buttons at the top of the screen, the small slider labels at the bottom, not to mention the choice of all lower case for the grayscale/color segment controller. The entire application appears to have been designed by committee.
There is one element though that I thought was pretty cleverly done, and that is the page layout and re-ordering screen. Using very, very big table cells, you can easily drag each page into the order required. I think the thumbnails are, perhaps, a little bigger than needed, but I thought the conception of how the page ordering works was pretty solid.
In the end, Scanner Pro provides some great functionality. It delivers that functionality in an ugly and somewhat confusing package. Do I recommend it? Yes. I can see using this whenever I'm on the go, to collect receipts, transform written documents, and so forth. My 3GS's camera with its capable focus can definitely make the best use of this software. This is a terrific idea and I love the ability to carry that functionality around with me on an iPhone.
At the same time, Readdle needs to step back and seriously evaluate their interface. Because that flawed interface is hiding a wonderful application that deserves better interaction. And if they don't do so, their competitors will -- as noted above, JotNot [iTunes link] will also do PDF conversion from the camera (single-page docs and whiteboards vs. the multipage support of Scanner Pro), plus Evernote and Wi-Fi integration, with a smoother UI and a lower price.