I don't know much about the context-driven school, but I am curious since Ward Cunningham is enthusiastic about these "young turks of testing". Brian Marick was there and participating in the Q&A too.
I think there is a good book to be written on "Planning Context-Driven Testing". I can see that one could come away from an initial discussion with impressions (prejudice) from the "old school" testers that context-driven means "unplanned". This is based on my observations of "old school" reactions to the agile movement of software development.
After Brett's talk, Brian explained in a small conversation that a way he plans for testing is to look ahead at all the potential hand-offs of software between people. (There are many kinds of hand-offs: from programmer-to-programmer, and so on, including handing off to the end user.) I really liked this approach.