I was at sears with my lil brother last weekend, and we came by an saw the xbox 360 20 GB HDD for a mere 8 dollars!!! he obviously bought it for his xbox (he has the arcade).
i say who cares about the format wars. i cant deny a 5 dollar deal on ebay for 300 in hd dvd. So i think if you find a deal then go after it, but NEVER pay full price for a HD DVD again.