I've noticed since first using YGN with Unity about a month ago that in pretty much every SDK revision there are multiple different copies of the PlayerIoUnityClient DLL. Surely this is a mistake? They should at least be identical files.
There is one in the Unity folder, and there are two different ones in the demo Unity project itself. I guess the one in Plugins probably takes priority for that case. There is also another copy embedded in the unitypackage file.