I think you can tell that I was impressed by the AirPort Express' many talents - good looks, excellent wireless performance and flexible feature set. The only missing functions are its ability to act as a wireless Ethernet client and WDS wireless Ethernet bridge. While they aren't required by most people setting up a wireless network, they would expand the base of possible Express customers.
The main dim spot in an otherwise bright outlook is the same as for most Apple products - price. I'm sure that Apple would argue that the Express has no competitors, and to some extent they'd be right - if you consider the Express primarily as an iTunes peripheral. But at current street pricing of around $120 (December 2004), it's twice as expensive as most 802.11g routers - both desktop and travel-sized, and remember, it only routes for wireless clients.
It's unfortunate that this price premium will make most Windows-world folks pass right on by. Because they'll be missing not only a nicely designed multi-mode 802.11g AP / router / bridge, but a product experience that's all too rare in the street brawl that we've come to know as the consumer electronics marketplace.