Edgy

After upgrading from Dapper to Edgy you have to increase the hinting style to Full in order to get the same look. On Kubuntu use the System Settings dialog, click on Appearance, then Fonts. Make sure that 'Use anti-aliasing for fonts' is enabled and click on 'Configure'. Now set 'Use subpixel hinting' to the appropriate value for your display (usually RGB) and select 'Full' for 'Hinting Style'.

Alternatively, have a look at your ~/.fonts.conf file and check that it contains the following:

 <match target="font" >
  <edit mode="assign" name="hintstyle" >
   <const>hintfull</const>
  </edit>
 </match>

If there already is a matching rule, which sets 'hintstyle' to 'hintmedium' or 'hintslight', just replace 'hintmedium'/'hintslight' with 'hintfull' and you are done. If there is no ~/.fonts.conf file you can just create one with the following content (that's equivalent to using the KDE tool and setting everything as described above).

<?xml version="1.0"?>
<!DOCTYPE fontconfig SYSTEM "fonts.dtd">
<fontconfig>
 <match target="font" >
  <edit mode="assign" name="rgba" >
   <const>rgb</const>
  </edit>
 </match>
 <match target="font" >
  <edit mode="assign" name="hinting" >
   <bool>true</bool>
  </edit>
 </match>
 <match target="font" >
  <edit mode="assign" name="hintstyle" >
   <const>hintfull</const>
  </edit>
 </match>
 <match target="font" >
  <edit mode="assign" name="antialias" >
   <bool>true</bool>
  </edit>
 </match>
</fontconfig>

Here is a related bugreport: [https://launchpad.net/distros/ubuntu/+source/fontconfig/+bug/63403] And a discussion on the forums: [http://ubuntuforums.org/showthread.php?t=244514]