Just just set up my Plextor PX-AV100U on my windows machine and plugged my amiga into it via composite connector. While the display was terrible (composite color bleed) it was rock solid even in hires laced with no flicker!
Because it only samples at 30fps it's probably not too good for games and demos but I don't know until I try.
I've seen a couple of A1200 s-video hacks. I believe they involve nothing more than two 100uF capacitors and two 75 ohm resistors (and cable).
Anyone tried it?