Since the resource center doesn't (yet) show recent changes to this API I thought I'd chime in that all of the EntityCacheState-related methods allow you to override the default of binary formatted save/read and instead use plain text. The ECS is in xml, so calling SaveCacheState with the option to save as text will do the trick.
Uploading into a different app, whether a DevForce application or not, might present challenges, especially if using DevForce or the raw DataContractSerializer - because of problems with "known" types.