Why does dragging a space in Spaces lag awfully

I find that killing the Dock only sometimes makes the problem go away. Usually keyboard input returns, but if I switch spaces using the keyboard shortcuts, the visualisation sticks around & keyboard input is stolen again.

What I have found to work is putting the display to sleep. I've had the bottom right corner of the screen set to do that for ages, so it's quite convenient for me. I've never had this method fail; once the screen is awoken, the problem is gone & doesn't return when I switch spaces again.

To me this suggests that the problem isn't actually in Dock, it's in the system's EventTap subsystem, the bit that lets stuff like Spaces, Screen Sharing, LaunchBar, & Spotlight take keystrokes before the focussed application gets them. I've actually experienced a similar problem with Screen Sharing, where the system whose screen is being shared gets its keyboard input mangled if a modifier key is pressed on the viewing computer & not released until Screen Sharing has lost focus. It's sort of the reverse problem, but it indicates that perhaps the Spaces problem is the EventTap framework getting stuck in a similar way, never sending the message that Control isn't being held down any more.

Although there is some very tiny overhead tracking the views of 4 or 9 windows - and your graphic card may be stretched to render more than X items at once - so it feels slower and renders slower animating the in/out of the spaces.

As far as the apps and the system - each window that is running simply gets coordinates. If it's marked on screen 1 and offset X and Y or no screen and X and Y - the system does no extra work. Each window must be tracked and only windows that are somehow visible get refreshed. Spaces adds no extra work or saves any work as far as the application is concerned.

If you tend to open more apps due to spaces organizing them - that will slow the machine down - but it's not inherent that spaces makes anything on the system or app level slower other than an added graphics drain to animate the changes. When you are not switching - it's probably faster since fewer windows have to draw into active viewports if you have less "on screen" at one point in time.