This surprised me. I bought a new 17" MBP because my late 2007 15" MBP is having problems. The trackpad has problems and the DVD drive won't work. I made a Carbon Copy Clone of the 15" MBP hard drive which is running Leopard. The new 17" MBP came with Snow Leopard. Just for fun today I decided to see if I could boot the new 17" MBP from the Leopard disk image. It works fine. I was always under the impression that when you bought a new Mac it couldn't be down graded. This 17" MBP likes Leopard just fine.
Terry
Terry