No HDMI only passes HDMI, I had an Iscan so I speake from experience, you can pass Composite and Svideo thru Component cables but not HDMI. For the record I have a non HDMI processor and just run HDMI direct into my Projector and run Component and S-video and Composite into my Processor and out to my Processor, its no big deal to have to push an extra button so save you money.
video processor & hdmi
Here's the issue. I'm getting a new pre/pro that is absolutely awesome, but it lacks hdmi inputs (which at this moment doesn't matter much). I was thinking about getting an external video processor and do all the video switching through that. Probably something like a DVDO iScan VP50Pro. Can I take the HDMI input into that processor, output video at 1080i through the component and get the sound output through the digital output? Reading the manual on the DVDO website made me no smarter...