Fonts have long been weak spot with Linux. However, nowadays there are many nice open source fonts available, and font rendering is pretty much on par with commercial operating systems. Most distributions do not ship with the best anti-aliasing options enabled due “software patents”. These patents apply only in United States. Rest of the world does not need to suffer due American patent madness so here is quick fix how to enable proper font rendering in Ubuntu: sudo dpkg-reconfigure fontconfig-config and select Native rendering from the next screen.
Open Font preferences from: System > Preferences > Appearance and select Fonts tab. Tune your rendering preferences, set Smoothing to Subpixel (LCDs), Hinting to Slight and Subpixel Order to RGB.