Updated at 10:05 a.m. on Wednesday: Apple confirmed that the new devices are true dual-band, meaning both bands (2.4GHz and 5GHz) and both networks (primary and Guest) offer 802.11n.
Without much ado, Apple has just rather silently upgraded its networking products, including the Time Capsule and the Airport Extreme, with two significant features: dual-band wireless-N and guest networking.
At its Web site, Apple states that its new simultaneous dual-band Wi-Fi allows for maximum range and compatibility, as the AirPort Extreme Base Station and Time Capsule work simultaneously on both the 2.4GHz and 5GHz bands.
However, it's unclear whether or not both bands offer Wireless-N (true dual-band) or only one band offers Wireless-N while the other offers Wireless-G (802.11g, hybrid dual-band).
Guest networking (or Guest Zone) has also been found in many routers from other vendors, most Wireless-N routers from D-Link have this feature. Basically it allows you to set up a separate wireless network that's isolated from your main local network. This is a great feature if you want to allows guests to access the Internet without being able to access your local network resources, such as your computer, printers, or the router's settings.
Other than that, both the new Airport Extreme and the Time Capsules have about the same features and design as their predecessors. The new Time Capsule also comes in 500GB and 1TB versions. This is slightly disappointing since you now can easily find hard drives that offer capacities up to 2TB for reasonable prices.
These new products are now available at Apple's Store with prices that won't reflect the current state of the economy.