As a Debian user that was something that I wasn't satisfied, and which Ubuntu did much better than anyone else, finally I found this link and I could match Ubuntu font rendering.

http://bit.ly/reTb4m

For me the real trick was:

echo "Xft.lcdfilter: lcddefault" > ~/.Xresources

Full URL: http://blog.andreas-haerter.com/2011/07/18/tune-improve-fedo...

I'm using Kubuntu, do I need to install the "freetype-freeworld" package?

No, you just need to execute this on a terminal:

echo "Xft.lcdfilter: lcddefault" > ~/.Xresources

And check the output of:

xrdb -query | grep Xft

KDE 4.9.5 it's already packaged in Debian, see: http://lists.debian.org/debian-kde/2013/01/msg00060.html, although those packages are targeted to sid, it works with testing after pulling a couple libs of sid.