This has been niggling at me across various distros (Debian, Ubuntu, Mint, Fedora... probably others). I'm on Arch now though (and planning to say
Font rendering in Linux is ok now generally, far
better that it was a few years ago.
It's just the fonts from the ms-fonts package render particularly badly (really visible on the 'k' of verdana on the body text of web pages for example. Arial is also bad and since many many sites specify 'Arial, sans-serif' or 'Verdana, sans-serif' they tend to get used a lot
So yeah, it's just those particular fonts which look terrible, the web looks great without them (I actually prefer a lot of the Free fonts). I just need to have them around for work.