I don't think mkvs are born with Macs in mind, hell, it barely runs on its birth platform sometimes. Just like Windows. :/ My brother the MacGeek uses VLC player, I think, but it's kinda sucky compared to good ol' MPC, and he doesn't watch anime so I'm not sure if it'd work on our codecs.

Memento is like the most detailed summary of everything (that Mentar and Garten watches), it's almost line by line. I hope you'll like it. :D