At the moment it appear as if Apple changed how OSX Lion might support AirPrint. I installed a fresh build of OSX Lion and ran AirPrint Activator on it.
AirPrint will make the necessary changes but AirPrint won’t work. Somehow Apple has changed how CUPS and Bonjour integrate. I will start to investigate what might have changed between the two and see if there is a way to get AirPrint to work again on Lion.
Until then enjoy AirPrint on Snow Leopard.
You can now grab an AirPrint Activator version that work on OSX Lion on this page.