Depending on a lot of version numbers, you may have to pass

          -Dswing.aatext=true
          -Dawt.useSystemAAFontSettings=on

to your JVM. I don't know why the default is "ugly 1990s-style", but those settings made Netbeans usable for me (for long enough to discover I still prefer Eclipse, except for the profiler).

AFAIK There is a setting in editor->Appearance->Use Anti Aliased Fonts and, as other commenter said Oracle JRE may have better font rendering than Open JDK.

On OS X you can add

apple.awt.rendering = quality

to the info.plist properties section in the .app Contents folder and it seems to make the fonts a little smoother as well.

Trying Oracle's JDK often helps with such things, as well.

I've found that using the "Nimbus" look and feel (Settings -> IDE Settings -> Appearance) and making sure "Use anti-aliased font" is checked (Settings -> IDE Settings -> Editor -> Appearance) do pretty well.

I am using an Oracle 1.6 Java on Ubuntu 10.10.

PyCharm and IntelliJ also seem to default to an "Alloy" look and feel on Windows, but changing that to the native Windows L&F vastly improves both the fonts and general appearance.

it looks pretty decent on Ubuntux64. Can you show an example?

I have an example from the Java IDE IntelliJ Idea from same company (PyCharm uses the same framework): http://img130.imageshack.us/i/screenshot6gw.png/ Does it look bad?

That's the maximum I could come up with after trying many suggestions. Still ugly for me. May be my eyes are sensitive but observe w, v and x. They're faded out. Also most letters look choppy for my eyes. I can't stare for long.