I have been using the Outlook add-in for a few years now and find it to be very helpful. I do have to agree with the earlier sentiment about learning GTD first though.

The Setting up for success webinars that Kelly did with the gentleman from Netcentrics are fantastic. Watching each of them really made me realize that I was not tapping the full potential of the software.

If you spend most of your day working in Outlook as I do, and have a good grasp of GTD the add-in can be a great addition to your toolbox.