The only negative issue I found was a that affore mentioned game of thrones mkv file. It still hasn't streamed properly for some reason, and with the k-lite codec pack installed, it played locally on the pc fine. Without it, it plays, but there is no sound at all.
We've already watched it in an alternate lower res form, but I'm keping the file to see if I can locate why it isn't playing back properly, or see if runnign it through a few utilities helps.
The last time I encountered something like this there was a mplayer (I think) update that wasn't playing properly with a new mkv encoding setting people were starting to use. Someone here pinpointed that issue back then.