I see where you guys are going with this.
Recording from an SDI player could be a VERY cool feature.
However, keep in mind that you're limited (in audio) - to stereo surround. In addition DVD-R media costs more than buying a new DVD copy of the movie...
I still think SDI out is also very interesting for using this unit as a Home Theater DVD source (even for recordings).
if this unit had more inputs, you could nuke one of those when adding the SDI input (e.g., the composite). I think each one needs its own A/D - so you can bypass just one of those inputs, not both Compsite and SVideo.
Problem is: RIAA will be on it like a fly on you-know-what...