This thread is about using the N800 as a PMP, so threads like "i don't really use my N800 for media" serve no purpose. I DO use my N800 for media. A lot. I have played mp4 videos created specifically created for the ipod and it played well. Search for ipod movie torrents. Torrents at thepiratebay.org play well. Divx files at joox.net all play well with mplayer. Files I encode play well, but self encoded files are highly variable. Sure, not all files will play but that is the case for every PMP. Even with a pc you might need to download a codec to play a video.

Mp3's play well for me. I use the default media player now that I don't have a lot of music, but I have used Canola and other media players. They all work well for mp3's and wma as well.