It's a definite improvement over Leopard. It looks the same on top, but under the hood it has had some significant tweaks. From the hour or so I spent using it, it seemed so much more smoother and faster than Leopard. It also takes up less space on the hard drive and Finder has been completely rewritten.
Fun fact: The alleged "Upgrade" disc is actually the full version of SL. Using the Chameleon bootloader you can use the Upgrade disc to install it on non-Apple hardware.
Fun fact: The alleged "Upgrade" disc is actually the full version of SL. Using the Chameleon bootloader you can use the Upgrade disc to install it on non-Apple hardware.