Apple suggests that Time Capsule - its newly-shipping backup device - extends the simplicity of its Time Machine backup component in Leopard. Plug it in, use an assistant to walk you through configuration, connect to the device or connect it to an existing network, and select its internal hard drive as the Time Machine destination for your networked Macs.
In my first pass with the backup appliance, I found that Time Capsule largely lives up to this expectation of simplicity, with a few glitches. I had to restart the unit more times than I like, fix a few configuration errors in its 'automatic' configuration, and deal with a glitch in getting Time Machine to select the right drive.
Perhaps most surprising about this combination of a Wi-Fi base station and internal network-attached storage (NAS) drive is that Time Capsule doesn't just allow you to back up to its internal drive: you can also perform Time Machine backups to drives attached to the Time Capsule via USB. This feature was promised before Leopard's release for the AirPort Extreme Base Station (2007 models), but later removed from Apple's list of Leopard features.
In a quick test of a full backup, Leopard transferred the first gigabyte of data over 100 Mbps ethernet to the Time Capsule's internal drive at about 16 megabits per second (Mbps), and to an externally connected Iomega high-performance hard drive at about 16Mbps. That's not speedy: I copied a gigabyte at 60Mbps over 100 Mbps ethernet using AFP between two Macs, and in under a minute to a drive connected directly to a desktop Mac (nearly 200Mbps). Still, the 15 to 16Mbps rate means that 100GB would transfer in 15 hours. Not fast, but reasonable for an overnight-into-the-next-day first backup pass.
Apple has extended Time Capsule's simplicity to its packaging and installation. The box, compact like all of Apple's recent packaging, contains just the Time Capsule, a power cord (Time Capsule's power supply is internal), a small envelope with an installation disc and a few booklets.
The new version of AirPort Utility that ships with Time Capsule - version 5.3, which is required to configure it under Mac OS X 10.4 or Windows XP and Vista - renames a few tabs and labels to allow Time Capsule-specific options. The Disks pane of AirPort Utility lets you erase the internal drive while renaming it. (The format comes with Apple's Secure Erase options: none, a quick zeroing of data, and 7-pass and 35-pass erases, which meet government standards for deletion.)
I chose a new option in the setup assistant that allows you to clone the settings of an existing base station. I had an 802.11n AirPort Extreme all up and running, so I chose that base station - the password for which was already stored in my Keychain - and had AirPort Utility copy its settings. After restarting, however, the Time Capsule lacked the static IP address I had manually assigned to the base station, and I had to set that part up again, re-entering all the details. I also had to confirm that I wanted remote management enabled, even though I'd confirmed that 'risky' option for the previous base station. The Time Capsule didn't initially recognise that an ethernet plug was in its wide-area network jack either; I reseated the plug and the device seemed happy.
Time Machine had no trouble discovering both the Time Capsule's internal drive and the one I had attached externally. One glitch occurred, however. I'd plugged the Iomega drive in after a Time Machine backup was underway to the internal Time Capsule drive. I canceled that backup and attempted to switch to the Iomega drive; no luck. I had to restart the Time Capsule to get the correct drive names and options to appear in the Time Machine preference pane.
When you start a networked Time Machine backup, the backup drive appears on the Desktop as a named volume (using AFP), and another volume appears called 'Backup of [Bonjour Name]' as well. The main drive shows all items; the volume named backup stores just the files for that computer. If you cancel a backup or when the backup is finished, that drive disappears as well.
Apple notes that Time Capsule requires OS X 10.5.2 for Time Machine backups; it won't work with earlier versions of Leopard. So you may need to plan time to download the massive set of updates - my Mac mini required about 500 MB of updates, including a 350 MB combo updater, after I installed 10.5.0 from a DVD; the 10.5.1 updater weighs in for most machines at a more modest 180 MB.