sudo apt-get install xorg-driver-fglrxfixed that right up. It's a little weird, but just roll with it.
sudo aticonfig --initial
Once the ATI driver problem is fixed, the installation goes swimmingly. I was a little troubled that it auto-installed grub over my previous installation of lilo (I miss lilo), but I was pleasantly surprised that the auto-installation of grub works better than lilo. And all this without my intervention. Seeing as my macbook pro is hardly typical linux hardware, I'm pretty pleasantly surprised over here.
Unlike with my vanilla installation of Edgy, sound (ALSA) is fully operational, as are the drivers for my ATI graphics card and synaptics touchpad. Feelin' pretty excited over here.