I don't have airport extreme, but I downloaded the update anyway, cause I might switch one of these days and it shouldn't matter but... it seems to. I was having a lot of problems with not getting good reception w/airport (it's the white snow station) & my Titanium PB, which have notorious reception problems (airport is in the other room). Now I have solid bars. Safari no longer requires me to click every URl twice. And so on.
The only explanation I can think is that there are some subtle improvements to the code that help w/Panther. Does that make any sense? Probably not, but why do I have all my bars when before I was lucky to get half of them? Crazy.
So do the update even if you don't have extreme. It may do nothing, but it won't hurt, either.