Ease of use
Speed / throughput
Configurability / networking features
A few years ago, we still had dial up, and were paying for a second phone line for the computers to use, with only one computer on the internet at a time. Living in a rural area there weren't any options for high speed, then this company named Omnicity came along, and for less than we were paying for the second phone line, forget about what we were paying for dial up, would let us have a Wi-max modem that would give us high speed, while not as fast a DSL or cable, it beat the pants off of dial up. Realizing this meant we could set up a network, and all of our computers could be on the internet at once, we shuffled off to the computer store to get some wireless networking equipment. By pure luck the Linksys WRT54G was on sale, and was chosen as the router. This thing has been rock solid for us for around 5 years now. The only reason I'd consider replacing it would be to step up to 802.11n which would be nice, but with our internet connection speeds, it's not worth the money to do it just yet. Cisco really did the home user a solid favor when they put this baby on the market.
Updated detailed review