This item describes the kind of range and issues surrounding the subject for a "regular" WiFi device:
http://en.wikipedia.org/wiki/Wi-Fi#ReachMy experience has been that the 2310 is a little lower in power than some other brands, but I have managed to get a decent signal out to about 50' through two wood and plaster internal (non-load bearing) walls - after which it drops pretty quickly. After about 80', another internal wall and a couple of kitchen appliances in the way, it was just about at it's limit.
Remember it's not just the router that matters. Your PC may have a low power card in it, and those with no external antenna may also report a lower signal than others. What you get will be highly variable. Move a sofa about ten inches and signals can improve or drop off dramatically and this is of course true for all lower power devices like WiFi equipment.
