After a couple of false starts earlier this year, I am now using GTDNext as my main task management tool and it is going very well. The program has forced me to think about how I manage my work, which has been a good thing.
One thing, though, that keeps me thinking that there could be a better solution is exactly what Armistead has asked about regularly: mobile app. The mobile web app is OK but a) it isn't available offline b) it is small and not as easy to work with as a mobile app would be. (just trying to tick or untick a check box, for example, is cumbersome). c) it is missing some functionality like moving a task into a project (although I did discover that you can drag and drop into a project that has an existing task)
I think the program is great, I've learned much about how I work or how I should work, and have appreciated the amazing interaction and support provided by James and his team. The mobile app experience is, however, very important to me. I travel a fair bit and really live and work on my phone a lot of the time.
Anyway, just some additional feedback. Keep up the great work.