I don't tag--I use the 'category' pull-down when I create tasks to make contexts. Then I just scan down the list of tasks when I want to work only in a specific context.

Here's my workflow:

- Check my email.

- Forward like crazy into Highrise dropbox+, so that the emails automatically populate the task list.

- If I write an email to someone that says "Dear so and so, I will do X and Y," I just bcc it into a Highrise dropbox+ and it automatically becomes a task.

- Every day I do a 'review' in which I go through the task list and add categories, clean it up, move things around, etc.

- I keep HR open in a browser window so I can add tasks directly.

This has actually taken care of nearly all my GTD needs. The one exception is really intense project planning; I have quite figured out how to do that yet. There is a lot of functionality in Highrise that I don't use at all--cases are a good example.

I think a lot of its value for me is dependent upon the fact that I don't have that many tasks. My work is very big-task focused and doesn't have much granularity, and rarely are there hard deadlines--they go on my calendar, anyway. So Highrise works great for me. Personally I'm glad it's not hooked into Basecamp, which would just be a source of confusing extra functionality for me.