I recently decided to do a fresh install of Leopard on my Macbook, I didn't add any of my files but simply downloaded and updated the system through software update. I then used grand perspective and the Get info windows to see the overall size of Leopard at 10.5.6. The total was 18GB!! This seems incredibly large, cant wait for Snow Leopard to bring a much smaller footprint to the OS! There was also 1.96GB of miscellaneous used space on HDD not quite sure what this was due to.