Apple Updates AirPort Express and Time Capsule
The most significant upgrade to both the AirPort Express and the Time Capsule is that both now support "simultaneous 2.4 GHz and 5 GHz dual-band networking." Dual-band networking is certainly nothing new; in fact, most 802.11n routers are backward compatible with 802.11b/g wireless devices. The problem is, the router will default to the speed of whatever the slowest attached device is running at. You could have five 802.11n devices connected to an 802.11n router, but if there is also just one 802.11b device attached, the router will default to 802.11b speeds for all attached devices--including the five 802.11n devices. What a simultaneous dual-band router can do is communicate with the 802.11b/g devices at their slower communication speeds, while separately communicating with the 802.11n devices at their faster communication speeds. It is truly the best of both worlds. Adding this capability to both the AirPort Extreme and Time Capsule make both of these products far more efficient in mixed-mode environments.
Both AirPort Extreme and Time Capsule also now offer an innovative "Guest Network feature [that] allows setting up a secondary network for friends and visitors with Internet-only access so you don't have to hand out your WiFi password." You can set up a separate password for the Guest Network or leave the Guest Network password-free. It does not appear, however, that you can set up user quotas, bandwidth limits, or QoS preferences for the Guest Network, so if you are concerned about your "guests" saturating your bandwidth or driving you closer to your service provider's bandwidth cap, then make sure to use this feature wisely.
Time Capsule is a "full-featured AirPort Extreme Base Station" that also includes a built-in hard drive for automated backups using Leopard's Time Machine automated backup application. It is important to note that while you can connect an external hard drive to an AirPort Extreme for network-attached storage (NAS), you cannot backup to such a drive using Time Machine. Time Machine only works with external hard drives connected directly to a Mac or via a Time Capsule device. (There are hacks available that can enable Time Machine support with NAS drives--including the AirPort Extreme--but these hacks are not supported by Apple and the hacks have demonstrated less-than-ideal reliability.)
The new AirPort Extreme is available now for $179. The new Time Machine is also available now in two different configurations: $299 for the 500GB model and $499 for the 1TB model.