As mentioned previously, I'm not a strict GTD follower, but I'm not far from it and I am an obsessive task-list-maker. It's the only way I reliably get things done.
I've been using Things from Cultured Code for a long time - long enough to have created and completed 3617 tasks, actually - and it has worked fantastically for me. I love the interface, and it works well.
However, it does not have cloud sync working yet (though I understand it is in beta), and even with cloud sync it doesn't handle delegation or 3rd-party information sharing well. That was never a problem for me before, but I recently has a new use case turn up as a requirement for me and my task list: I needed to provide visibility into my tasks to 3rd parties.
To me, that means that 3rd parties should be able to look at my task list at any time, with no extra effort on my part. Requiring effort on either my part or the 3rd parties part would be too inefficient for something as constantly used and updated as my task list. Further, it should be possible to swap tasks back and forth with people if I want, with a minimum of effort. Things simply can't handle that.
Some features that Things has which I must maintain are full-featured offline functionality, a feature that eliminates most issue-tracking software like JIRA. I must be able to automate task intake from Mail.app to the task list as I had before. Finally, I must be able to access and modify my task list on my phone, in sync with the list on my desktop.
For all these reasons, I've decided to migrate to Toodledo - it appears to satisfy all these requirements, with the possible exception of good Mail.app -> Toodledo integration, but I'm aware of a couple ways to do it already just not quite as good as I like yet. At present it appears I'll use Toodledo's web site for 3rd party access, their iPhone app for phone access, and TaskSurfer for a desktop client. I'll continue to use Mail Act-On for Mail.app integration and I will either use Toodledo's email interface for task queueing from Mail.app, or I'll figure out how to drive TaskSurfer via Applescript.
The next couple posts will detail the scripts I've written in order to implement the migration from Things to Toodledo so that I don't lose my existing data from completed Things tasks as well as Things in progress.