Signal variance is nothing new. I remember personally noticing it in late 90's that with my GSM (900MHz) phone, moving it on table just for about 5 centimeters could bring it down from full signal to no reception at all. Of course with analog radios you also notice how easily signal changes with location. If you've been ever playing with TV antenna in in bad reception and so on. Moving your hand in other room might block TV signal or make it crystal clear even if you would make there's no connection what so ever. With 2.4GHz people often forget that interference from other sources can significantly contribute. So signal quality and signal strength aren't same thing at all. Getting to the root all these things require professional, which I'm not. So one type of measurement defined as "signal strength" probably misleads you badly. Is it a good idea to select a wifi channel that doesn't have any other wifi boxes? Well, the reason might be that the channel is totally overpowered by local wireless CCT or phones. That's the reason why nobody's using it for WiFi and then you think it's a great idea to select a free Wifi channel?
Radio stuff is (truly) really tricky. With higher frequencies it's just like light. Why some things are in shadows and some things are well lit?
I'm in a relatively large appartment building.. I can see about 20 other wifi options in my area on my laptop... fortunately, my signal quality is significantly better (higher end asus, with shibby tomato) spent a fair amount of time tweaking the settings a bit that seem to work very well for me... I can keep signal on my phone across the parking lot (I'm facing the pool, which is adjacent to outside parking) ... no wifi really gets into the garage though, but cell phone signal does...
It's really wild how a foot or two difference could make all the difference in the world...
