happy upgrading, enjoy the fabulous kde4!
writing a thesis right now, no time and wish to risk anything.. i'll wait for the moody monkey (?) instead.
ps: only bug that affects me now is that, every some 10 bootups, kde starts complaining about "removed sound devices", and indeed audio does not work on some applications (using pulseaudio?), e.g. flash. rebooting again is generally sufficient. let me know if this ever happened to you with karmic, and if it still happens with lucid.