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."
Windows Photo Gallery came with Vista PCs. It was the basis for the new, improved version, Windows Live Photo Gallery. However, downloading the beta doesn't overwrite the software on your Vista PC (the plain vanilla photo gallery)...although it should!