I've also used Konsole as my primary terminal application, but in recent Kubuntu releases it became slow.
Yesterday I switched to good old xterm with screen:
xterm -bg black -fg grey -fn -*-console-*-*-*-*-*-*-*-*-*-*-*-* -geometry 166x45
and in xterm I start screen with 10 sessions.
Now everything is fast again. :)
