"1> Aspect ratio control --- in general, is it sufficient? Can you squeeze a 4:3 source for anamorphic projection? "
Yes, I think so. I have use it with the Panamorph with no problem, you can rezise and center the picture without problem.
"2> DVD --- I'd like to hear how well it handles scaling for DVD sources from component video... and if you have SDI available, it would be cool to hear about that too. "
Yes, it can handle component from progressive dvd, but I think it looks better using 480i.......no I don't have the model with SDI
"3> HDTV --- I'm told it can transcode HD component signals to RGBHV or it can pass native RGBHV. I'd like to hear how well it performs in both categories."
Component to RGBHV? yes, I've made a test using the sony 9000 progressive dvd as a source to th 406 and then I use the 480p RGBHV output from the 406 to the Faroudja
5000 and scale to 1080P with the Faroudja
"4> Are there any output resolutions NOT listed on the specs on their web site? Specifically 1365x1024 and 1366x768?"
406 do not do 1365 X 1024 @ 72Hz but only @ 60Hz
I will add one more question: Is the 406 the perfect scaler?
I don't think so....while wathching concerts dvd the picture break for a very short moment from time to time even using it @ 60Hz and with a crt pj. The adjustment for bright and contrast are no so ease to set correctly, there is a point where the picture is correct but if you move the setting just a little you can loose the pludge using AVIA dvd. I got the best picture using the AVIA gray ramp and ajusted using a scope at the output of the 406
Federico