OS X Leopard's Time Machine works on Airport Extreme routers as of the last firmware update, but TidBITS found out directly from Apple that it's an "unsupported feature." What does this mean to you, the guy who wants to use Time Machine on the Extreme you purchased last year instead of shelling out a couple hundred bucks for a Time Capsule? It means you should upgrade to the most recent firmware now, before Apple updates again and takes out the feature. It also means that you should check the internet whenever there's a firmware update from now on to see if the feature's been removed before you update. To be completely safe, just save a copy of the most recent one somewhere. [Tidbits]