Divx is a modified Microsoft mpeg-4 codec. I've found it looks as good as quicktime or windows media under simular settings. The filesize is sometime smaller, sometime bigger then QT and WMV. Most of the movies I download off the net (movie trailers, game trailers, movies made from game engines) are in divx. I prefer Divx over Quicktime because QT requires the annoying QT player and I can't play QT movies with my TV out.