So, it turns out I hadn’t quite fully given up on running Ubuntu after all. I found this thread on the Ubuntu support forums that discusses how to get the broadcom chipset (the brains behind Airport Extreme) to speak friendly-like with linux.
Here’s what’s happening, according to the thread:
The reason the card shows up but doesn’t work is because ubuntu is only distributed with its driver (so it can recognize it) not with its firmware (so it can USE it) for legal reasons. However you can take the firmware out of the windows drivers and put them into ubuntu and make the card work!
This inspired me to use the Ubuntu .iso I’d already burned (back when I was still excited) to boot as a live cd & see what I could get up to. It’s pretty cool to see my pb boot into linux again. Yee-Haw!
Most of the instructions for enabling my wireless card seemed to work, right up to the part where I have to reboot to see if I can connect. Because I’m using a live cd to boot, all changes I make get wiped on shutdown 
So now I’m left with a decision to make: Do I keep going and re-partition my drive to install Ubuntu (which involves re-installing OSX, too) on the chance that my wireless card will work? Or do I stay quit and spend some quality time with, um, a book or something? What’s this worth to me?
I guess, now that the live cd is working, I’ll play around and see how Ubuntu stacks up. Then I’ll know if it’s worth the probable hassle.
Oh, and by the way, I’ve been writing this from firefox in Ubuntu (via an old ethernet cable). Yippee!
Using the Ubuntu LiveCD you can resize your MacOS partition and install Ubuntu without having to reinstall MacOS. I found that the ubuntu installer balked if your set up the new partition manually. Just resize the MacOS partition and leave free space at the end of the drive. Then tell the Ubuntu installer to partition and use the free space (NOT THE WHOLE DRIVE, WHICH IS THE DEFAULT!) during the install process.
Wow, thanks for that, Chris. I’ve actually been toying with the idea of throwing Ubuntu on my PB again recently, since I now have a new MBP to use for work. This is *really* useful info for me!