you're right, it doesn't natively play mkv's, but the conversion of the file takes less that a minute, 10-15 seconds most of the time, and i coincide it with copying to the usb drive at the same time so in reality it takes no extra time, as the encoding it simply changing the container, so it takes the time it takes to copy to the new location only.
much as i'd like a new toy in my life then, at the moment this doesn't seem like something i need.
I'm actually watching less and less downloaded stuff now, with SKy HD its all on there with very little delay these days, have swapped to watching House, 24, Lost, gossip girl, 90210, flash forward and kitchen nightmares as it all airs the same week.