I am using Prophet 2004 and the add-in I use prophet for all sales related things like proposals, quotes, follow up calls etc. As it manages these very well. This I do so I don't end up with a project list a mile long as I would have to list each sales opportunity as a project.
As prophet uses all of outlooks native tasks, contacts etc I find it easy to blend it in with GTD add in. For example a follow up call task in prophet gets the action @calls etc. Write proposal gets @office etc.
GTD Add-in projects I use for anything else sales budget, larger proposals where I am putting together a bid, where I need to bring in outside help, i.e. engineering, production etc.
To date this has worked wonderfully for me. You might not find that you need the add-in if majority of your time is on sales opportunities, and you don't have a large list of non sales opportunity projects.
Other than that I love Prophet, after working in Act, and outlook Business contact manager (BCM), this is the most logical and least intrusive solution.
Hope this helps
