Hack-a-Day has a nice first impressions piece on the Xbox 360 from a hardware hacker’s perspective. Their conclusion:
I think the best plan would be to wait till next year to make the purchase: the console will be cheaper, the selection of games will be broader, used games will be available, you’ll know the Playstation 3’s features, the Xbox 360 games will be making better use of the console’s power, Microsoft will have most of the bugs ironed out and you might be able to run Linux.