AirPort Utility 5.3.1 is now available for Mac OS X 10.4 Tiger, Mac OS X 10.5 Leopard, and Windows XP and Vista. This is the first time that Tiger and Windows users can simply download the utility and install it. Up to now, you had to use an installer CD from supported hardware to obtain AirPort Utility, or install Leopard. AirPort Utility can configure any AirPort Extreme Base Station, AirPort Express Base Station, or Time Capsule. (The update was unavailable for several hours after it was initially posted, reappearing by Wednesday morning.)
The software first appeared with the 802.11n AirPort Extreme Base Station model released in February 2007, and the AirPort Express retail packaging was updated by mid-2007 to include it as well. AirPort Utility shipped as part of Leopard and comes with Time Capsule as well. The software is more neatly designed than its predecessor, AirPort Admin Utility, and reveals more configuration options even on older models.
AirPort Utility can optionally install a software agent that runs in the background and monitors the network for the addition of USB drives connected to an AirPort Extreme Base Station or Time Capsule and for problems with base stations on the local network. It can also check automatically for updates to itself and firmware updates. AirPort Utility makes it much simpler to roll back to earlier versions of base station firmware when you encounter troubles.
The most notable change starting with AirPort Utility 5.3 is the ability to set the Bonjour name of a base station separately from its descriptive name: choose the AirPort pane and in the Base Station or Time Capsule tab click Edit beneath the Name field. Formerly, you could set just one name that was used for both purposes. The descriptive name is used to identify the base station within AirPort Utility, but also to name its attached volumes.
The Bonjour name is used to advertise the base station across the network and could be changed to something short and sweet or long and more technical. Wide-area Bonjour configuration is now found in the same place that you modify the device's Bonjour name. Wide-area Bonjour is ironically not yet widely supported; it's a way of publishing local networking information to a DNS server.
I discuss AirPort Utility, wide-area Bonjour, and other AirPort-related subjects fairly extensively in my book, Take Control of Your 802.11n AirPort Extreme Network.