RE: looking at signal strength
I mentioned this earlier in the thread, but I think it's worth repeating.
If you have an Apple Extreme (and a mac), you can see signal strength via airport utility 5.6 (which runs fine on Lion; the newer one doesn't have, or has hidden, this feature). You can download the utility version 5.6 for Lion from apple. (If you have an older airport express as I do, you need it to configure that)
It's in the Advanced Tab, Logging and Stats section, click the log and stats button.
These signals strenths are much more informative than the bars. It also shows you connection speed. For example, my MBP connects at 130 mbit, but new ipad only at 65 (probably its limit) close to the router. So, the ipad might drop from 65 down to 24, but you won't see a difference if you're running speedtest app (assuming your broadband is < 24), but you do care in the use case of moving large files in your home network.
Ron