After I added a layout to my drawing, I noticed that all operations in the main screen slow down considerably, presumably because all layout viewports have to be updated as well. This is particularly annoying when moving objects, which is very sluggish with the object leap-jumping behind the cursor. No doubt users with more powerful machines than mine will be less annoyed.
I keep my layout details on a separate layer, and I noticed that switching off the visibility of that layer returns Rhino to the speed previously experienced. Closing the Layouts window has the same effect.
So, I am wondering if it needs to be that way, redrafting the Layout viewports could at least wait until the move command (or any other command) has been completed. Better still, updating the Layout viewports could be updated only on activation of the Layouts window.