Well comming is too personal, since I don't use KDE, but anyway, there's a $500 bounty sponsored by Lucas Murray to implement Fluxbox like tabs in KDE :) .

Tabbing is a nice feature that allows you to tab windows together. Tabs can either be embedded into the window’s titlebar or they can appear as little tabs at the outside of a window. The position and size of the outside-tabs are customizable.”