forgive my ignorance i currently run windows, however i know i will soon be making the switch. i am considering waiting for leopard to buy a mac, but what i would much rather do is buy now, then upgrade to leopard when it is released. when leopard does come out, will there be an upgrade pack - something to move from tiger to leopard? or will tiger need to be removed before leopard is installed? if tiger does have to be removed (or if there is an upgrade route), will apps/files stay intact or will they all be lost in the process?