Not sure about Mandriva being a "killer" each to their own. KDE4, been using it for a while. first on Suse as a try out, and to be honest it really peed me off.
It comes as standard in Mandriva 2009 (my real world distro) which i installed recently so i decided to get stuck in. Once you get over the different way of working with the Plasma workspace, its actually very good, even with the widgets and the cashews
It starts to become intuitive very quickly. Love the Dolphin file manager (no more konq) and the way it previews files.
Its the first incarnation of Mandy that i can actually say is point and click software. Even the PLF repos can be added from zarb.org with no more than a few clicks, no cut and paste into a root terminal, and of course all the stuff you really need is there. i.e, flash player, libdvdcss2, win-codecs etc.
Ah! rambling on a bit, i'll go now.