Lightroom was having trouble saving some metadata changes to some files. Convert to dng seemed to fix them. Also i think that any xmp changes (lightroom adjustments) will get saved inside the dng rather than a sidecar xmp file, which is preferential to me. Finally, i am not 100%, but i think that the embedded thumbnail that lightroom creates (eg, the nice looking post edited file) will also be used by media center or other external apps when opening the files.
This seems to be the case for all of my raw anyway. For the jpegs it has made them unreadablein Media Center
