I just ran into this short article that explains some of the long-term benefits of applied critical thinking and the tester’s perspective. Stick with it through page two; it’s worth it.
In the mean time, I’m working on a one-page article that provides a brief explanation of topics in Agile-Testing. If you’re interested in peer review, drop me a line, or leave a comment with your email address. (You may want to hide it, EG matt dot heusser at gmail dot com – etc, to prevent spam.)