They've really done a bunch of pretty hard core development on it. All of it really Google focused. They've integrated Google Gears, they've got a Google Gadget, Google Maps integrated for tasks with locations, and integration with Google Calendar. They've got a great mobile site, and integration with IMified. You can send emails to create new tasks, and also have a Windows Mobile application that synchronizes with the site.
My initial reason for hopping on board was that they are one of very few, if any (that I know of) todo lists that provide the ability for me to share my todo list with other users. This is most helpful with the honey-do list that my wife shares with me. I can add items to it, view it any time I want, and print it off for the weekend so I can
reluctantly happily do my chores.
My only beef with it, is that the task management screen needs a bit of help. It's obviously AJAXified, and has the usual stuff you've come to expect out of these interfaces.
However it's got a couple shortcomings. When you switch window focus, and you are currently editing a field (for example the task name) the field saves. This is a pain because I often have to translate due dates from my school calendar to the task list, so I'm switching windows. I'd love it if it didn't automatically save when the window loses focus.
The second issue, is that the list has a really weird edit concept to it. As you mouse over items in the task list screen, it shows the details in a panel on the left. Each item in the list has a checkbox next to it, and in order to edit an item, you have to check the box.
That seems a little weird to me. You can check many items, and that leads to a pretty arbitrary decision as to which one I want to edit. Seems like they could add an "edit" link for each of those items, or somehow disconnect the checkboxes, which are good for doing things like marking a bunch of items completed, or changing the priority for many items, but not good for acting on individual items.
Anyway, I'm very pleased with this todo list app. It's been sooo helpful in organizing school, and work and home.
What todo app do you use?