kppp will not work for regular users unless root is allowed to send a window to the display, i.e., I have to say "xhost +localhost" in order to start kppp. I like the original kppp access restriction vie /etc/kppp better.
making kppp suid root is a potential security hole, especially as one can script programs to be started arbitrarily during the login phase. 'su' can be used to become root before starting kppp, or if you have the latest pam and consolehelper packages, this should all be automatic.