One promising feature that wasn't mentioned in Apple's keynote speech about Leopard is a feature that was originally described on Apple's Leopard Bootcamp page:
Curiously, the feature was removed from the page since it was posted, but a Google cache remains available.New, faster restarts.
Leopard brings a quicker way to switch between Mac OS X and Windows: Just choose the new Apple menu item "Restart in Windows." Your Mac goes into "safe sleep" so that when you return, you�ll be right where you were. It's much faster than restarting the computer each time. Likewise, a "Restart in Mac OS X" menu item in the Boot Camp System Tray in Windows makes for a faster return to Mac OS X. With Windows hibernation enabled, you can pick up where you left off.
Update: One comment indicates that this features has indeed been pulled:
I have it on good report from someone attending WWDC that this feature has been nixed.
He mentioned this feature to the Apple BootCamp build engineer. Who responded that this feature will not be supported. The engineer then called the Apple BootCamp program manager who "freaked out". Within an hour it was removed from the website.