I puchased an Apple Wireless Extreme Base Station when I bought my 12" Powerbook. I couldn't be more pleased. The range is very good, both my mac and my 2 pc's work with the Airport. One of the pc's is connected via an ethernet cable to the base station and the other pc is using a USB wireless external box/card from Compaq. The 12" Powerbook has a Airport Extreme card in it.
My range improved with the latest software upgrade to 10.2.5 so I am very pleased. The Airport Extreme Base Station is the one with the WAN Port, LAN Port, Antenna Port and a modem. (I connect via Dial-up since I live in a very small town in Texas!)
Jim