Just wanted to let you know that you're not the only one researching this issue. I've got a component->VGA transcoder box based of one of the newer national semiconductor chips that does 480p, 720p, and 1080i, but no 480i over component. My transcoder worked fine with my Comcast cable box in 480p, 720p, and 1080i modes, but it had issues when running 480i from my 10 year old Sony DVD player.
Hopefully we'll have an answer in a week or so once component cables are available at retail. I'll post my success to this thread then. If it doesn't work, it may be a nice time to upgrade my display to something better.