Rule #2: It never goes as far as they say it does
Perhaps the biggest frustration that new wireless networkers encounter is finding that the range of their wireless network is nowhere near what they thought it would be. Part of the problem is the same "bigger numbers are better" approach that is used for throughput specs.
But where no manufacturer would dare quote a number higher than 54Mbps for unenhanced, i.e. standard-compalient 802.11g throughput (since that number is set by the 802.11g specification itself), there is no "standard range" number for 802.11 products, and manufacturers have much more leeway in the numbers they advertise.
As a result, the range numbers you'll see quoted from various manufacturers vary widely... so widely, in fact, that there is another rule for using them:
Rule 2A: Don't buy wireless equipment based on a manufacturer's range specifications.
I've come to the above conclusion after testing many wireless products and finding little correlation between the advertised and actual range. Unfortunately, the only effective way to know how a piece of wireless networking gear will perform is to try it in your environment. It also helps to have a basic knowledge of the way that high frequency radio waves work and basic range-enhancement techniques. See our Wireless LAN Performance Improvement Need To Know for more info.