This looks very interesting. I read David Allen a bit ago and purchased the Outlook plugin but have yet to fully implement it at work.
I use google for most everything but my work contacts and schedule. The problem is that task list is lacking to say the least. I like the idea of having everything connected the way it is in Google, and I hesitate to start using a separate task system.
I hope Google has there eye on one of the web based systems and snap them up so the task list gets much needed improvement.
I will have to take a closer look at GTDagenda. Nice review.