mkv is the most hyped container out there. It is mostly used as a container for avc + several sound tracks + subs, but all of that is already covered by a standard mp4 container. mkv does have some wicked sick "features", like having different parts of video in different format (?) but tell me how many on this planet do need this feature? And guess what, it doesn't come for free, but complicates code needed to support this format.
Unless there are license issues, I don't see ANY reason to prefer MKV over MP4 container for average Joe. :crazy: