So I wired this thing up to my XBox today and did a quick test. I've either got something wired wrong (I wired all this a long time ago, so not sure). Or the bios I have flashed to my XBox currently doesn't play nice with component video output, as I'm getting video but the colors are not right. I'm also getting some faint scrolling lines on the output. A symptom of things not being 100% right I'm sure, as the video output I got from my PS2 with this thing was absolutely beautiful. Anyway:
I'll do some trouble shooting in the next few days as my time right now is super limited. Set my Box to output both 480p and 720p and both convert fine as far as video resolution goes. Both settings output a beautiful picture, besides the colors not being correct.
The only bad thing (I had suspected this beforehand) is that the XBox's boot and bios screens don't display in progressive mode. So you'll get no picture at boot up until a game loads if your VGA monitor does not support 15khz VGA signals. 3rd party dashboards such as Evox or UnleashX DO display in progressive though, so if you've soft/tsop modded you'll be fine once your 3rd party dashboard loads.
More testing... tomorrow...