If there is one app category overpopulated in the AppStore that is productivity tools. I'm pretty sure you even have a ToDo app installed right now on your iPhone, but they all follow more less the idea of collecting information and ticking actions as you complete them.
Dunnit [iTunes Link] by Runloop is a ToDo app which adds a social element to the mix: The tasks completed will earn you OpenFeint points and will unlock achievements, making it the first productivity app to use social networking to motivate users to complete their tasks.
At launch Dunnit will display a list with the items to complete, the task list, where you can tick as done the activities, edit, or just see your overdue or upcoming projects. Every item has a headline and description (notes) and the option to set priority as well as set recurring tasks.
Even though it might not be part of some people's GTD routine, it is a much demanded option in mobile devices, since you won't have to enter the information next time you need to complete that task. Dunnit will sort the tasks on a timeline looking at the due dates. Again, GTD purists might not agree, but I suggest to always set a completion date for the app to display your next activities efficiently.
Activities can be organised with tags, which are used here as a context field, although you can also add your own ones. For this type of applications I've always found more useful to sort tasks according to a location: Things I can do when I'm at home, at work, on the bus… these days you can get a lot of things done on the phone while I wait for the bus for example. Combining the task list timeline will give you an overview of your day/week, while the tag view is the ideal for actually get cracking on them.
One of the critical part of a productivity app like this is input information. Who wants to use something tedious and complex which only makes you lose time? Dunnit has a simple approach, allowing you to add new items independently or multiple tasks at the same time. In fact it is similar to others like Things and OMNIFocus in this sense, while other apps like 2Do are more extensive and allow you to enter more metadata with the tasks. As a novelty, Dunnit also offers the option to use the clipboard to create a new task, pasting it directly and saving you some taps. It's not rocket science, but I thought it was a smart touch for people that don't want to type. In fact, it encourages the user to add new tasks with the clipboard, making easy the collection part of your GTD workflow.
In the graphic department, went for the standards Apple UI adding some wooden touches. There is no wow factor, but there are small details pleasing to the eye such as the shadows, grey areas, subtle reds for overdue items and most remarkably the wooden background on the task list view.
Dunnit has all the capacity you would expect but the lack of some advanced features like nesting or synchronization at all will leave some pro users out. However, I do recommend do give it a go, since finding an app that adapt to you can be very difficult. For my personal use, I miss the option to create groups, nested lists and arranging multiple tasks at the same time.
I really liked the simplistic approach for this todo list with its non-intrusive UI, ease of use and specially the tutorial included as a task list to discover when you first launch the app. The developer is very active with the community and has dropped the price very recently.