I have a AirPort Express (the little Macbook power supply-sized ones – I forget if the UFO looking ones are called AirPort Express also) and [assuming the power supply doesn’t go out] I love the darned thing. It’s great for portability!
I take it with me when I go on the road and have instant wireless. There’s absolutely a market for something like that. The Airport Extreme is nice (not that 802.11n will work with my Macbook) and I’d really like the ability to attach an external drive to it (even more so if it would properly host my iTunes and/or iPhoto library) but it’s too big for travel.