I had KDE4 installed on Ubuntu 8.10, and recently installed Kubuntu 9.04 on my x86 desktop and have had none of the problems you describe. System Settings all work fine - but I have never had much joy with Network manager.
My Kubuntu PPC 8.10 -> 9.04 upgrade locked me out of my Mac G4. If Kubuntu is the bastard sibling, Kubuntu PPC is disowned bastard sibling :-(
