Comment 34 for bug 299330

I accidentally submitted an incomplete comment there... I have this issue in 64-bit Karmic with Compiz.

Compiz users: make sure you check your settings! In the config manager, go to the Static Application Switcher->Behavior tab, and make sure "Popup Window Delay" is set to 0. I think the default value is non-zero.

Even after doing that, though, I still have just enough of a delay to be moderately annoying.