Jeff Croft: You win the gold star. I went to the Appearance preference pane and changed Font Smoothing to "Standard - best for CRT." At first it didn't do anything, then I rebooted and now everything is elegant again. There are other settings too which I didn't fiddle with, "Light," "Medium - best for Flat Panel" and "Strong." I suspect that when it was on "Automatic" previously it was selecting "Medium." Anyway, in my experience all this stuff is subjective; everyone sees it differently. I actually know a friend who thinks that Windows' font smoothing approach -- ClearType, or whatever it is, I don't recall -- looks great. A real person!
Yes, ClearType looks very good on an LCD screen, which is what it is designed for. Likewise, "Medium" looks IMO best on Mac LCD's, since it starts doing subpixel rendering at that level, which improves the perceived horizontal resolution by up to x3.