Xbox High Definition Pack
I live in the USA and this works perfectly fine with my new high definition T.V. It is amazing how much better high definition is over s-video. However the picture of the unit on this page is not the one you recieve. You do get Microsoft version but it is just one cable. It still has optical attached to the part that plugs into the back of your xbox. However I paid $40 but whatever they don't have these units anywhere in the USA. I tried ebay and got a generic one that was horrible. For $40 for high definition this is worth it. Now I have surround sound and high def. Awesome!

Works with PAL Xbox units.
i'm in Australia and it works fine - several of my friends have imported these from asia and they work without any issues. whether or not actual game behaviour is effected i have no way of measuring, but even if purely for the sake of having clear image transfer without bleed (composite/s-video), then it's absolutely worth it.

as for TOSLINK - well, it's TOSLINK - no major gripe against the product, more the brilliant person who created it as it tends to be a bit of a flimsy connection. nothing inferior about the port in this unit though.