When I try to force-open a VOB file with QuickTime Player (Mac OS X 10.4.1, QT 7 Pro) I get the message "QuickTime cannot open the file: "VTS_02_2.VOB" it is not a file that QuickTime understands (-2048)".

Perhaps the MPEG-2 (or some other non-standard) component is required as well?

I just tried this in 6.5.2 on Mac OS X 10.3.9, and it seems to work there too.
In response to the previous poster, I do have the MPEG-2 component for QT, so this may have allowed me to do this. In case it's not clear, you do have to go through the "Open..." dialog box to have this work.

I also tried exporting the movie to animation codec using QT Pro, which it allows, but the video fields in the MPEG-2 make the result look pretty poor.

I'm sure mpeg2 component is required. At least it was for me.

Perhaps the MPEG-2 (or some other non-standard) component is required as well?

Yes, the MPEG-2 component is required for this hint to work.