Apple's Time Machine and a Laptop

I think I'm impressed with Apple's backup solution in it's new operating system Leopard coming out on Friday. Time Machine keeps track of files that change and copies them to a backup disk every hour. Every day it compresses them down to a single changed file a day and keeps track of them. The result is that if you lose a file or a change in a file, you can go back in time to find what you want. The UI is very Star Treky but the integration of "search back in time" in the Finder and Address Book is very very slick. Type what you're looking for then scroll back in time until it appears in the window.

So this seems like might work great on a desktop machine. Just connect a backup drive and point Time Machine at it and you're set. But I use a laptop, sitting in a comfy chair connected via wi-fi to the internet. Remember Apple's iBook laptop was the first laptop with wi-fi built in. So how will I use Time Machine? It seemed obvious; Apple's AirPort Extreme base station lets you connect a disk drive to it making it available over the network. At 802.11n speeds this seemed great as long as you didn't travel much. However now it seems Apple has doubled back on Time Machine and AirPort Disk. All references on Apple's site to using Time Machine with an AirPort Disk have been removed. Now why would that be? If it's really not supported, I'm very disappointed. Connecting an external drive to a laptop all the time seems to defeat the purpose.

Update: Apparently it will work with a network drive that's connected to another leopard machine. So if you have a mini with leopard and an external drive you're fine. Then again, I'd rather pay $200 for an (overpriced) AirPort Express for this task than $600 for a Mac Mini if that's all I'm going to do with it.