I have a chart with 90-degree rotated category axis.
This works fine in FireFox 12, but in IE9 (64 bit) running on Windows7 I am getting hierogliphics. I have done nothing special with the font settings in the browser, so it seems the default for charts is an Arial or Verndana type font.
Horizontal labeling is working fine. (the data is remotely driven, so creating a JsFiddle would take a little work).