" Anything will screw up your transfer speed. Assuming that you are in the 2.4Ghz band (.11b/g), the microwave, 2.4Ghz phones, bluetooth devices and other networks will all make your transfer speed go down."
Which is why you spend some time setting it up right. All my WLAN's, which number in the hundreds, are stable in all respects. Give or take the odd few. It's a fair statement in general terms to say wireless is basically unstable because the gear is cheap and anybody with a few bucks can go buy it and set it up. What is not accurate is to say that as a blanket statement. Wireless LAN's are a buyer beware market. As long as the buyer is knowledgeable, thorough and efficient WLAN's are perfectly dependable and stable.