Yes, I guess it is. However, the other alternative is to become a client (time/money issues for me - also have already attended GtD seminar) or have someone help me develop a template and then get my IT people to agree to let me use it (they are not real receptive to that sort of thing).
So... right now I use the two programs along with a Palm. Basically, it means that the Next Actions from emails need to be entered or copy-pasted manually into Outlook. (I should also say that there is talk that we'll switch to Outlook, and that has influenced my decision to use both programs as well). I get about the same number of NAs from email as I do from other sources though, so for now it's not as big of an issue as it could be.
I do use the add-in, but not as exensively as I could since its usefullness seems to hinge on email.