Originally Posted by BobbyRS
It isn't really that it is hard to support as a container. Due to MKV's openness, it will depend on what is used within the MKV container that could be new and challenging to support. You can still have an MKV file that contains MPEG-2 for video and MP3 for audio; not really any different than a typical AVI file. MKV's ability to use compression like H.264, AC3, DTS (and more) is where many portable devices will run into trouble with being able to handle. I think the Cowan A3 fully supports MKV.
Exactly, as long as it's standard video / audio any player could possibly handle it. But the extra material can vary between files, that's why its hard to support it 100%. In the beginning even media players for PC had problems with the container. I'm unsure if the A3 fully supports MKV, maybe it does, then it's good for those that watch anime