I am on a Debian 3.1 sarge system on AMD athlon xp 1500+ with a 2.6 kernel and i just upgraded to kde 3.3 from 3.2.3. at first the quality of the images on the panel and in the taskbar were the same as in 3.2.3 however after the third reboot or so the fonts and panel/taskbar images were horribly bumpy and not at all anti-aliased. i changed no settings.
actually, even though i HAVE libjpeg installed (i fixed the font problem in the settings) kde was not able to find it so i recompiled QT with support for its jpeg, gif, mng and so on and now the image quality is how it was before.