OK, This is really just another "note to self", but someone might find it useful:
% mencoder {PATH}/VIDEO_TS.IFO -ovc copy -oac copy -of mpeg -o {OUTPUT FILE}
That's it (It runs quite fast due to the lack of any transcoding). This assumes your DVD only has a single title, but I suspect it's possible to select which track of a multiple-video image somehow (I might update this article if I ever need to do this).