keep your tiger discs around in case you have some major leopard issues. However, you will probably be happy with it. When upgrading, immediately install 10.5.1 (from what I've read anyway). If you have a Yamaha Cavit, it won't work on Leopard. I found out the hard way. Read the list of applications that won't work, make sure none of them are currently crucial for you. Further updates of leopard will probably bring compatibility/function back.