I have a Palm IIIx and have installed the GTD add-in. The sync works beautifully using only the Chapura pocket mirror standard that came with the Palm. The only thing I had to do to get categories to link properly was to (1) go to the chapura site and download the free upgrade to the standard version, and (2) follow the directions on their web site for configuring the hot sync conduit to preserve Outlook categories. It works like a charm. Each Next action category maps to a Palm category and the Projects list maps to a "Projects" Palm category. The only thing you can't do on the Palm is view things by project or assign a project. You have to do this in Outlook once you do a sync.
One caution using this approach is that the Palm is limited to 15 categories, so that measn 14 Next Action categories plus the project list.