The problem with that one is that it doesn't do any scan format conversion. Most monitors won't display 480i so you won't be able to view the XBox dashboard or GC games that aren't progressive. The upside is that you will be getting native progressive for games that support it.
I know, but it's much more affordable then the $800 Component input board for the computer. It could do all the scaling and changes to display it, but component to VGA isn't worth that much to me.
If you want a good TV->VGA box
I already have an ATI Radeon AIW card to do this, and the quality still dosen't match my Dreamcast with actual 640x480 output. It is slightly better then a normal 27 inch TV, but not by much.
$250 seems worth it to me since it's only $50 more then the Audio Visionaries box, and will switch automaticially. (Thus eliminating the need for a cheep VGA switcher, or doing a cable swap every gaming session.) Plus, it will still serve a purpose down the road, where as buying a Gamecube or XBox VGA solution will limit me to using them with those devices only, and not other component capable devices.