Have you attempted to review extensive MKV playback with feature films as you did with tv-show episodes since you mentioned at Archos Fans that the Archos Android, basically, has issues playing video with files that are over 3,500kbps?
Can they REALLY updated resolution capacity in a firmware upgrade?
4.4GB movies at 2h length or more seem to play mostly fine. I tried a 1h45 Ghostbusters 4.4GB MKV, it played kind of fine for 4-5 minutes until the first fast action scenes happen then it drops frames and the synch goes out a bit.
Archos "just" needs to improve bitrate support by about 50% on top of the about 3500kbit/s it does now for MKVs and I think most TV episodes of 400-800MB per 20-30 minutes will play fine even for faster action scenes and I think most movies 90minutes and longer at 4.4GB should play smoothly.
If you will want support for 4-8GB movies, those are generally a bit over the 5000kbit/s as far as I have seen so then Archos probably needs to double the bitrate efficiency to about 7000kbit/s or more.
Chengbin and others will be able to provide more details on what exactly is supported. I can only really test my complete MKV collection from next week when I receive my new Fonera 2.0n so that I can setup Samba/Upnp shares with all my big files instead of transfering them one by one over USB.