Have you or your team looked at the platforms offered by companies like Netkey? They offer content distribution and quite a comprehensive suite of security and deployment tools. We've been looking very hard at them for some time during our project but haven't made up our minds yet as to whether to implement their software or not with our kiosks.
Thanks so much for the work you've put into this series. I'm currently working on a similar project with a retail customer facing kiosk. This contrast between SteadyState (which I just ran across this afternoon) and GPO was just what I was looking for.
This is probably a very simple question, but what methods are you looking at (or are you) to log in a restricted domain user account on startup?