it can play mkv now, cept that it has to be the right type. mkv is simply a container. if the file itself is supported, it'll work. typically most mkv files floating around are h.264 which works, but typical sound is ac3 (5.1ch). unfortunately pb doesnt support ac3. aac tho it does. if the mkv is h.264 video and aac or mp3 audio, it'll work now.
as for a player that plays unsupported types, i believe some converted android apps might. otherwise, what i've been doing is re-encoding my previously ripped movies from ac3 to aac using handbrake.
and just for reference, heres the supported types. bookmark it! its a good one to have.
What is the best method to determine what types the video is? I have an old version of GSPOT but it doesn't seem to work very well. Gives me no info on the files in question. After i run them through handbrake it tells me they are h.264 and AC3. Thanks