>>16
Obviously it's a matter of opinion but there are some solid rules of thumb about type design. For example, letters shouldn't run into each other. Read
The Elements of Typographic Style.
On computers, good subpixel rendering algorithms are important (until computer monitors hit a higher PPI then we can forget about them). There's also ordinary anti-aliasing and hinting (which basically lines the curves up on a grid). Here's a nice article:
http://www.microsoft.com/typography/TrueTypeHintingIntro.mspx
Text generally looks ugly on a default X setup because 1) you're not used to it, and 2) Microsoft and Apple have all the patents. Freetype supports various types of subpixel rendering and hinting, but they're generally not as attractive as their Windows/OS X counterparts. It's also a fucking mess and a nightmare to configure.
Fortunately, a few people have written patches to make Linux fonts look more like they do in Windows or OS X, or at least less shitty. A good one is Infinality:
http://www.infinality.net/
I really hope X dies soon and Freetype with it. I want Wayland with sensible font formats (i.e. not PostScript Type 1 and XLFDs), and a font configuration system that I don't need to learn an XML schema and software library to use properly.