US Discs
You all seem to forget a little thing called 'Region Coding'. It was the one sticking point with DVD's which made quite a few people lots of money to 'region free' your machines until most DVD manufacturers built in a simple remote control hack.
HD-DVD's are, by design, region free. I also happen to have a region free DVD player ('adjusted' Panasonic DVD-R).
So I can buy my daughter 'Ratatouille' which is already out on DVD in the USA and play it on my DVD player here at 480p. I don't think it's finished in the Cinema here in the UK. And although it's rarer now, it still happens quite alot, and I still buy the odd DVD from the USA, or HD-DVD.
However if I had a PS3 or UK Blu-Ray player, I couldn't buy the US Blu-Ray copy of Ratatouille and play it in my player because it won't play. And worse luck if I try to amend or 'hack' the player to do so, it reputedly has the option to brick the player as the player occasionally authorises the playback online and updates encryption keys.
Compare that to the HD-DVD of Shrek 3 which I've also had for a couple of weeks also from the USA, which comes out next week, and plays quite nicely at 720p on my Xbox360's HD-DVD drive (as does the full series of Heroes which I also have on HD-DVD which has been out in the USA for months).