While the new Apple 802.11n Airport Extreme has some new, first-generation hardware issues (as well as draft, pre-n standards issues) that must be resolved in a few months with an update revision to the product, it actually seems reasonably priced for the money, especially given the connectivity and faster streaming capability for Apple TV that you get.
In addition to the Ethernet WAN port, it has multiple Ethernet LAN ports and of course, you can connect that USB hard drive to add network storage (Unfortunately, it is missing gigabit Ethernet, a very odd omission for NAS and I hope this also will be corrected in a future revision update). Most importantly, the new Airport Extreme will give you the network throughput to stream iTunes movies and video.
Finally, while it is $40 more expensive than the old 802.11g Airport Express, it is about $70 less expensive than Apple's old Airport Extreme (though it does not have a hardware-based dialup modem, as did some "g" Airport Extreme models).
Still, this new Airport Extreme does not have the combined, analog/digital audio (optical) connector for audio speakers. For this reason (and because the old 802.11g Airport Express price now has been reduced to $99), I think that a new, less expensive 802.11n Airport Express also must be in Apple's pipeline.