So I have two reasons to wipe the machine and put Linux on it: getting up-to-date browsers again, and getting any sensitive data off it before the machine dies completely.
For the past few weeks, I've been downloading Linux distributions, concentrating on ones and trying them under VirtualBox. A few were then burned to DVD and I tried installing them.
Ubuntu installed well and supported the Macbook's hardware fine. But I really disliked the Unity GUI, which wasn't easy to figure out -- I never figured out how to edit the contents of the panel, for example -- and it doesn't encourage using alternate things like KDE.
OpenSUSE's installer is impressively professional looking, and I really liked the KDE desktop that I installed. (To me KDE still seems to be the desktop that thinks about its users, not abstract goals and redesigns.) But the installation on the actual Macbook didn't work. After about 100 packages, the pre-installed scripts began reporting errors and aborting the installation of that package, affecting critical pieces like grub-install and linux-desktop-kernel. I found forum reports of similar problems, reporting that re-burning the DVD fixed the problem. But I burnt a second DVD that passed verification immediately after burning, and passed its own integrity check, and this second DVD still had the same errors. So regretfully I had to move on from OpenSUSE.
Finally I tried Linux Mint, using its XFCE desktop. It installed smoothly from the DVD and everything worked fine out of the box. All I needed to do was to fine-tune the trackpad sensitivity a bit, turn off transparency in the terminal application (what are they thinking with that default?), and install a few things such as Emacs and git. The resulting desktop is clean, the OS only takes up 4Gb of disk space, and I'm all set.