It looks to me like the state property is actually required to be of String type. In particular, trying to use the Enum type from dm-types seems to be a complete fail; see https://gist.github.com/3410344 .
Off-hand, it appears to me that the property's accessors are overloading the accessors created by state machine.
It's a problem for me since I'd like to retrofit state_machine onto some existing models. I've tried using the :namespace property, but that doesn't seem to help; it's not a problem of the events, but of the states and their values themselves.