I'm hacking Class::Workflow into Mango for the checkout page flow control, mostly so people can just tweak the workflow rather than hacking around code.
Class::Workflow is Mooseified and I need some custom state classes. It seems only natural, if not safe to code them using Moose as well.
It's only a matter of time until I start the conversion, but I'll hold of until it's actually frigging finished and tested. :-)