Well, I haven't spent any time writing Outlook add-ins as I'd imagined.  Instead, here's something positive and something nagative from my experiences so far with Getting Things Done and the Outlook add-in:

On the plus side:

• Contexts are great.  Putting things onto a todo list and pre-categorizing them based on the context in which you want to do them is great.  This is super helpful.  When I have a few quiet hours in the morning, I can do the things that require concentration.  When I'm between meetings or only have a few minutes free here or there, I can work on lots of those thigns that take 5-15 minutes.  For me, I've created two key contexts that I use for work @small and @medium.  @small things are the ones I can do really anytime (when I'm at a computer -- which is almost all the time I want to be actually working).  @medium ones are the ones that take more then 5-10 minutes.  Those I actually try to schedule onto my calendar into slots that don't have meetings.  I've just started this new approach (using TaskLine to lay out the tasks automatically for me).  We'll see if it actually works.

On the negative side:

• Lower priority items can drift forever.  This is one of the things that I wanted to solve when I started using GTD.  The basic problem I have is that something gets assigned a low priority when I put it on my todo list.  And it really is low compared to other stuff.  Then I work on my high-pri items all the time.  And I have enough high and medium-pri stuff to do that I never get to the low priorities.  Which is fine and appropriate for a few days or even a week.  But sometimes these things just keep slipping out forever.  Very bad.  Maybe some way to raise the priority of things as they age?