mathtext alignment

I noticed that when I do something like


that the text is rendered with small variation in the alignment of the
characters. In the example linked below, the lower-case letters in the title
appear to be offset.

I end up exporting .eps files, and there the rendering is normal. Has anyone
else noticed this effect?

(By the way, nice work on the log-scale formatter, John. Now the tick-label
fonts match in a semilog plot.)