Just because I don't use Ubuntu regularly at home, doesn't mean it's the same at work ;-)
For some reason, I just cannot get Arial to look good on my Ubuntu box at work. I've tried all the various fontconfig settings, and nothing looks as good as how it looks on Windows. The closes result I've gotten is to turn off anti-aliasing, and use full hinting. That makes it look like Arial from 1995. But even then, the spacing is wrong1.
Anyhow, so until they fix it, I want to turn off Arial, and use Bitstream Vera Sans instead. Sure I could delete the font, but this is exactly what .fonts.conf is for. Here's the little piece:
<match target="pattern" >
<test name="family">
<string>Arial</string>
</test>
<edit name="family">
<string>Bistream Vera Sans</string>
</edit>
</match>
You can pretty much use this trick with any font.
1 I believe this is a long standing freetype bug. It also appears when you try to use fonts like MS PGothic and MS PMincho using their embedded bitmaps.