I'm hoping that they continue to support the G3 FW machines, like they did with the OS X 10.4 build, if only to maintain the OS X Server I use for most of my server-side activities. I absolutely love the server package, but it doesn't require all that much processor power for what I do.
I plan to upgrade across the board, though, on the G4 PB, the Sawtooth, the B&W server and the MacBook Pro. Apple upgrades are generally flawless for me and I appreciate/use the new features once I figure them out... Spotlight alone was worth the upgrade to 10.4.
Timothy