I'm using KDE 4.2.2 with most KDE applications installed, and there will be more than 5 icons when I type "kon" in krunner.

In KRunner, after I type "kon", then type "t", notice that the icons disappeared with an animation. You can use Backspace key to remove the "t" and then press the "t" again to see the animation carefully.

Animation can be cool, but for low-end computers it is a waste of time and hurts user experiences, in my opinion the applications like krunner simply should response instantly without any animations.

Is is possible to disable the animations so that I can improve the responsiveness of krunner?

Sorry but it does not appear possible to disable the animations, although KRunner now lists items completely differently in KDE 4.3.