ListBook is yet another to-do app with an engaging interface that is easy to use. Of course it exists in a sea of GTD (Getting Things Done) apps, but I think it is staying above water. The app is US $1.99.
ListBook is universal, supports notifications, and allows you to send your lists via email, but the list is not converted to text. The receiver must have ListBook too. That's a bit nasty.
Items can be tagged with colors, names, or descriptive icons. There is no limit to the number of lists, and you can easily swipe left and right to change lists, or even delete items. It's all very intuitive. Any items that aren't completed show up as a badge on the icon, alerting you that you have items yet to do.
The latest version claims the iPad and iPhone version can sync, but for the life of me I can't figure out a way to do that and nothing on the developer website that I can find explains it. I've contacted the developers, but no answers yet. (Update- the developers have now added a page to describe how you can set up the sync function.)
I started using the app right away, so it really doesn't require instructions. I like the app enough to use it for my various listing tasks, something I haven't used an app for in the past. I fault it for the confusion about syncing and inability to mail your list to anyone but another ListBook user.
You can see some screen shots below.