Jackilyn Hoxworth figured out how to revert the dock in Leopard back to something more familiar:

Type this into terminal to get the no glass dock.

defaults write com.apple.dock no-glass -boolean YES
killall Dock

I haven’t yet upgraded, but the new design elements seem to be pretty attractive. When you spend all day in front of a monitor, though, I guess you tend to get used to things a certain way.

How-To: Get Rid of the Glass Dock in Leopard – Link