I think the keynote was meant to give us a teaser - but stayed tuned for more technical details in the future. You may also want to keep an eye on Channel 9 and developer blogs as they will likely dive into some of the more technical aspects of Windows 7.
In the keynote, they did say that -
# Windows 7 has a reduced memory footprint and they’ve reduced the disk I/O reads “substantially.” In the demo, a 1 Ghz/1 GB RAM netbook had 500 MB RAM available after boot.
# Better power management in Windows 7 means longer battery life for notebooks and netbooks.
But that was about as technical as it got...this is more of a "first look."
You may want to check this out too, a great Q&A on Windows 7: http://www.neowin.net/news/live/08/10/28/live-qa-session-on-windows-7-pdc-build
Also, Ed Bott's first look: http://blogs.zdnet.com/Bott/?p=575