A little late, I know, but I have it in a 700 Square foot apartment in New York City, and its worked fine for me. I VERY rarely take the laptop into the other room, but when I do I have not had any problem.
I have the e3000 with 2 Xbox's, 1 PS3, 2 Laptops several iphones and ipod touches and everything seems to be running fine. I had to research and learn how to Port forward to take care of the moderate NAT issue on my Xbox, but now it seems to be running really fast with now connection issues or lag.
The Cisco E3000 works fine with my XP SP3 desktop and laptop computers. Also works great with Vista and Windows 7. Fast and easy to setup all wireless items PS3, Xbox, Tivo, printers, desktops and laptops.
You do need a separate modem between this router and the internet line.