I've just posted up my summary of day one at WinHEC 2004. Mainly focussing on the keynotes of this morning. Unless someone else posts the Half Life 2 demo video then watch out for it coming soon to Neowin :)
Keep an eye on the blog for some interesting Longhorn builds tomorrow as well as day 2 coverage.
News source: Neowin's WinHEC 2004 Blog