I finally got around to flashing my WRT54GL with the rather spiffy openwrt firmware (White Russian 0.9 release). Considering I had been intending to do so ever since I got the thing early in the year, this represents a rather impressive feat of procrastination on my part (although not yet an awe-inspiring feat, such as my intention to finish working through the Communication Theory text book I bought while doing my M.)
The process was competely painless. In fact, it was so painless I'm almost feeling cheated. Isn't getting Linux running on exotic hardware the way you proven your geekiness? In addition to the extremely simple install (point router at firmware, press upgrade, wait), the upgrade process retained the wireless network settings, so I didn't even have to configure anything to get my wireless network going again.
Now, having finally flashed the the thing, I can move doing a proper compartmentalised wireless setup up my todo list. Check back in six months or so.