for any who are interested,
the SlackBuilds for kde-4.0.1 on Slackware-12.0 (and -current) are pretty well stabilized.
you can check it out with svn from http://batts.mine.nu/pub/src/SlackBuilds/kde4/
and its up to you to download the kde and deps source 😉
if it breaks, let me know, vbatts(AT)batts(DOT)mine(DOT)nu