Some Type 1 fonts, particularly URW Palladio L, look rather ugly when rendered on-screen in various programs. In particular, the letter height is inconsistent.
The header text is Nimbus Sans L, also a Type 1 font; sometimes, it looks acceptable, but sometimes its baseline isn't clean.
I have this problem in most programs. OpenOffice and AbiWord both display it with URW Palladio. I similarly have problems with Nimbus Sans embedded in PDFs displayed in Evince.
Any suggestions as to how to fix this? Settings I can tweak somewhere to make it work properly?
Tinkering with the rendering settings on the font tab of System>Preferences>Appearance should let you fine-tune the appearance. The hinting (instructions on how to best suggest the shape of the letters at low resolution) on some fonts doesn't work well with the default settings.
This Ubuntu Wiki entry has some explanation of font settigns in Ubuntu.