We've found the Airport Extreme and Airport Express to be reliable during four-years (Extreme) and three years (Express) of use. Also, setup is simple -- the best I have seen in such network devices. And the Express travels well too. Some purchase an extra Express, configure it to join any existing network, and use it to extend the wireless range of networks in hotels or other venues when traveling. Also, the Airport Express wireless music system is very, very nice -- and affordable given what it delivers.
However, there were about 800 Express owners (the last time I checked online) who all reported similar component failures during the 12-20 month time frame. I believe all units that failed were made in the same factory. In fact, both our Extreme and Express routers died simultaneously at about 38 and 18 months respectively, as did a Netgear 10/100 router and a hub on the same network. They did not simply stop working entirely (which would have made troubleshooting a breeze). Instead, it now seems that all these devices started failing during the same five- or six-week period. During this time, the network and Internet connection continued to function intermittently, which really made troubleshooting the problem all the more difficult. We never found out exactly what happened, and for awhile, I even thought it was a Comcast problem. But in the end, I concluded that a summer power surge probably fried all these network components. After troubleshooting with a telephone support tech, we took the problematic Extreme and the Express routers into a Genius Bar appointment and the tech tried to get them both working on their store network. When both failed there, Apple replaced them on the spot (with rebuilt units). A year later, both still are working fine.
Fortunately, we had purchased the Airport Extreme with a PowerBook, and so the tech at an Apple Store said it would be covered by the PowerBook's three-year, AppleCare extended warranty that had been purchased at the time of the sale. He allowed this, even though that three-year warranty had expired two months earlier, because both were on the same invoice and because we had formally reported the intermittent behavior to Tech Support before the warranty had actually expired. So, Apple replaced the Airport Extreme without hesitation, and then went the extra mile, and replaced the Express as well, even though it was purchased separately and was long out of its one-year warranty.
We've always gotten great service, support and warranty coverage from Apple, and I've only had one other product fail (a G3 desktop computer) since becoming a customer back in 1987. Even then, after three attempts at a video signal repair, Apple just called one day and offered to replace the entire computer with a newer G4 model that then was shipping (since the G3 desktop had been discontinued). However, I realize some online forums contain many examples of frustrated customers who do encounter problems. My advice, purchase their extended warranty when possible (especially for laptops) and carefully document any and all problems through Tech Support phone calls and/or at the local Apple Store.