I am doing something similar, but using the .NET built in JSON DataContract serializer. The things I've hit so far:
a) Anything other than a 200 return will raise an exception (understandable), but not give you access to the returned json (bad; e.g. 403 responses often have useful data with them) b) dates, times, timespans use an MS extended encoding (\/Date(xxx)\/) that simplejson cannot generate on the server side (I've posted an ugly patch here on the list before) c) dictionaries have a super-weird encoding from the .NET side; I opted instead to send a list of keys and a list of values from the server. These may or may not be relevant to jayrock.
