The DVP642 plays anything that follows MPEG4 spec, including DivX 3/4/5 (and 6) and XviD. The compression algoriths are all different but the decoding methods are identical. The decoder doesn't care about how the file was compressed (DivX/XviD, anything in-between, including MP4) it just wants to know what formula to use to decode each frame. The same formula works for each specific compression method because all MPEG4's have things in common, such as a standard header which contains the bitrate and audio track sync marker.
Any DivX DVD player will look at any MPEG4 file and see a bitrate and a keyframe and be able to decode anything from there. Interesting thing about MPEG4 is it has no traditional 'keyframes' because the bitrate is used to determine how to sync video/audio and to search through frames in the file and keep everything smooth and artifact-free. This also makes it streamable presuming you compressed it with the ability to stream (must have presumtual header information encoded, an easy option to turn on)
DivX 6 adds new compression methods such as tri-cubic, a better 'movie-mode', grit removal and higher bitrates. It also features the ability to embeed menus and 5.1 channel audio, but this is not a feature of the format itself, just additional information the DVD player will disregard. It will still play the initial video stream and 2 channels of MP3 audio.
-Tim
p.s. The DVP642, and many others, are firmware flashable. If you look at divx.org you'll see these are officially licensed DivX players, and it is in the DivX organizations' best interest to have these players support the new formate's features. DivX 6 menu and 5.1 support will be added to the DVP642 (and others) in the future. BET ON IT.
All in all, this thread is as much a scare tactic to thrawt people from buying DivX-DVD players as much as Bush's War in Iraq. It's a lack of information. HDTV MAN, although I have nothing personal against you, is warning people about what he worries about, a worry that only exists because of his lack of knowledge over the MPEG4 format. There is no worry man, MPEG4 is here to stay, and was built to be universally portable. It's already 8 years old and even the earliest codecs can still read the newest XviD 1.1.3 files and DivX 6 with near-perfect decoding quality/performance.