For those who are interested I now have a working integration of PersonalBrain and David Allen's Getting Things Done methodology. In truth I don't know where to begin explaining how it works - it's all in my brain! However I'm happy to answer any questions from fellow GTD'rs.
The basic components are:
1. Next Actions and contexts are tracked in Outlook
2. Projects and Someday/Maybe items are tracked in PersonalBrain. This allows me to get much better context for a Project. Projects get linked to a concept, GTD Horizons of Focus and other goal related items as appropriate.