As you might know, Debian's KDE 4 setup creates and uses ~/.kde4 instead of ~/.kde . After being using both of them for some time (I keep using twinkle, konversation and katapult, as krunner is too slow, and the great Amarok), I decided to move ~/.kde to ~/kde-old and softlinking ~/.kde to ~/.kde4.
I had to copy the configs of konversation and Amarok (not katapult as it's easy to configure, and twinkle uses ~/.twinkle), but so far it turned to work great. Great I say? better! Now katapult and konversation uses the brand new icons of KDE. Links in konversation opens with the apps configured in KDE 4, and I can even jump between different parts of flac files (perhaps that's another issue, but at least it works now :-D ).
Maybe I shoul ask Sune and start trying to port OpenSuse's tool for migrating KDE's setup to Debian.