This is a really good post on some of the issues with Cairngorm that most people are not aware of:
http://blog.iconara.net/2008/04/13/architectural-atrocities-part-x-cairngorms-model-locator-pattern/
Cairngorm has achieved popularity by virtue of its early entry into the Flex framework ecosystem and not necessarily because it's the best. There should be at least one significant entry into this space very soon that is going to really shake things up. Framework competition is good!
