Longhorn is supposed to be built on XML, so because of this, your systems will be able to run up to 5 times faster. Also because of this, Longhorn will support harddrives 1 Terrabyte and up.
I also found a page describing EVERY aspect that we currently know about Longhorn, I'll try to find it and post the link.
EDIT: Found it:
http://www.softwaretipsandtricks.com...omments&id=220