Right now, I'm using DataContractSerializer along with DataContractSurrogate to provide serialization descriptions for NHibernate proxy classes (as described in http://timvasil.com/blog14/post/2008/02/WCF-serialization-with-NHibernate.aspx).
I'm really interested in switching to protobuf-net to serialize my data using protobufs, but I can't seem to find a way to consume the DataContractSurrogate's. Without this feature, I'm dead in the water for serializing NHibernate dynamic proxy classes that derive from my model classes.
Im not a NHibernate expert, but in v2 there are a few things designed to cater for this scenario; foremost there is code built in intended to recognise NH proxies and treat appropriately (in particular, not complain about unknown types).
I will read the linked article, though; without more NH experience I can't be sure that the current approach is sufficient. I would also be more than happy to receive any test cases I could use to prove that it meets the need.