When you travel just use Leopard
or you can still use the 9600m in windows, it will just give you an hour or so less battery depending on what you're doing. This is software related (or so I've heard) so this can always be updated by a firmware update.
Hopefully Windows 7 and/or Snow Leopard will take advantage of both video cards and might give better battery performance. I plan on getting both when they come out next year