Kevin, I just did a Search on the word: Outlook AND Add-In. I think the thread Getting Things Done Outlook Add-In v PDF (Workflow Proc.) will give you enough information for a good start. The second post in the thread by mochant also suggests you do a search on his blog (an excellent resource, by the way).
I bought the add-in about two years ago, just after I discovered the GTD methodology. Since I use outlook, I thought it would be the fastest way to get up and running. I still think so.
I use the add-in every day. I think it is worth the money.
The add-in lets me focus on the work I do, not on the system. Since I did not devolop it myself, I don't spend hours and hours tweaking it (which I probably would do if it were my own, homemade system).
It has limitations, but I have found that practicing GTD within the limits of the add-in is an efficient practice. The add-in automates a few basic tasks like delegating a next action to someone else and creating the @waiting_for next action with a consistent format of delagatee and original date. The add-in also sets up task views to let one see actions filtered by project or by context. I use the 'by context' view frequently to see what I could work on next. I use the 'by project' view weekly as part of my weekly review.
It has tools to help administer a project list and an someday/maybe list.
I think it also gives one the ability to learn GTD without also having to learn to set-up and maintain a system.
There are keyboard shortcuts that let me capture an unimportant task or errand quickly and easily, freeing up my mind for the more important things. An example of an unimportant task would be 'buy tarp to cover wood pile.' The same shortcuts let me capture important tasks, too
I can sync to my PDA so I can review my next actions and checklists while away from my desktop PC.
On the negative side,
1) There is always room for improvement - new features, ways I wish the add-in functioned.
2) The web site forum is pretty lame. The developer of the add-in does not typically participate, so there are many unanswered posts.
3) Some users have had problems during installation.
4) You really do have to conform to how the add-in works. It won't bend to fit your will.
5) There is no version for a PDA. Nor is there any easy way to keep two computers running the add-in in sync.
6) Since the add-in takes care of many things 'behind the scenes' I had trouble trusting it in the beginning. I can see that if I had manually copied an email to the @action folder, I would trust that it was there. With the add-in, I don't participate in every step so I must trust that the steps were done properly. Of course, the automation is the main reason to use the add-in so I wouldn't want it any other way.
IMHO it's kind of pricey at $69 for a product which has had limited growth (much like Actioneer) beyond a bug fix here and there.
I was able to immediately cut my inbox processing time in half. As I get more familiar with the add-in I'm cutting back the time I spend processing e-mail further. Before I was spending 2-4 hours a day just processing e-mail. If I failed to get it processed, I'd miss an assignment or let a project fall through the cracks. I'm now able to process e-mail in two 20 to 40 minute sessions (with occasional abberations) Not bad for $69 IMHO.
The add-in does have its limitations, and there are some key features I wish it would include, however, I definitely think the add-in is worth checking out.
As mentioned above, the add-in does help a lot with the process of coverting emails into action items. More important to me is the way that it helps with the weekly review. With the add-in, the review of my project list is automated. I just switch to the task view, and use of of the four GTD views created by the add-in. In that view, I can highlight each active project and ensure that there is at least on NA for each project.
Admittedly, the support presence on their forum has been pretty quiet but in my personal experience, no direct request to their support team I have made has been treated differently than Michael's. Always responsive and, given the vagaries of what can possibly go wrong in Outlook, always very accurate.
I use Outlook as my key tool for implementing GTD and the Add-In is invaluable in keeping my inbox empty and my tasks organised under categories (especially those arising from emails recieved).
I'm currently experimenting with syncronising my Outlook tasks with MindManager/ResultsManager to get a better visual overview of my tasks. Demanding, but rewarding when it works: see Marc's updated review of ResultsManager at http://office.weblogsinc.com/entry/1234000697025444/ .