Answering a question (link with more info & comparisons to OPlayer) regarding AVPlayer running on the iPhone 4 (released in Summer 2010), I've quickly tested the MKV playback in the player on my 4th-generation iPad touch (released in Autumn 2010) to find out whether the question is right. (After all, AVPlayer(HD) is probably THE most recommended generic video player, particularly for MKV playback.)