Just an improvement of Windows XP with new "Aero" interface and graphical installation insted of the ususal 98/XP installation. Too annoying security system, bad integrated graphics drivers. I like the faster boot time though. Personally, I prefer the new Mac OS X Leopard, which will be available for Intel-based proccessors too. It's scheduled for release between 7th and 11th of August, if I'm not mistaken.