Again, RDP isn't used for streaming video. That being said, MKV isn't supported natively in Windows/WMC, so its sort of kludged together with unofficial WMC add-ons. That probably has something to do with some of the problems. But the Echo's problems with MKVs appear to be more an issue of the Echo struggling with H.264 playback.
Anyways, hopefully Ceton can deliver with this Android environment. As I said before, I think this is really the best thing we could have hoped for. I certainly don't regret returning my Echo, since who knows how long its going to take them to get this working (and what its features/limitations will ultimately be), but if it ends up working well I may give WMC+Echo another chance.