I'm not saying its a big one, but there would be a slight performance hit; at the exact same time your trying to open another program.. This could be part of the reason it wasn't added along with the fact that the new program should ideally be drawing your view away from the receding menu anyways, possibly distracting you. (once you open a program, you don't need to think about the start menu anymore and it moving will just draw attention/thought So I am personally against it.. but if it were Optional of-course I have no counter-argument