i think you should definetly buy now!
i'm going to be buying one of the new macbooks soon. i'm eagerly awaiting switching from PC to mac and originally decided until leopard was released to buy one. then when all the rumours came out about macbook updates and what not i decided to wait.
yes a new aluminium case would have been ace! yes a superdrive would have been good! but it's still a good update, and i doubt it'll be updated anytime in the future, probably around spring time. i suppose you could wait until then to buy a better, more updated macbook, but then by that time you'd probably be thinking 'but if i wait until next november, they'll probably update the macbook again!' 😛
technology changes and with months your always going to have an out of date machine, just go for it and buy one. i know i am 🙂