ServiceStack/ServiceStack.Text — pull request #192 by awr (2012-09-17 22:39:15+00:00)
Title: ExpandoObject deserializer including primitive type deserialization

I realize this may go a bit against the design decision you mentioned in http://stackoverflow.com/questions/8848958/servicestack-text-serializing-dictionaries (I assume because of the potential speed loss rather than the design choice of strongly typed DTO?), so I'm not sure whether this fits in with your goals for the project.