Yes, if I am using a word processor and want to pull up the calculator I don't want to lose sight of the document I am working on. Its nice that the old start menu didn't hide everything. Then when I get the calculator I want to see the number from my document -- don't want it taking up my entire 25 inch screen.
I think if Microsoft made more of an effort to encourage users to filter the start screen by typing then this would all be less of a sticking point for people. If I have a word processor open and I want to use the calculator I press the windows key and hit c-a-l-c-<enter>. The calculator is up on the screen alongside the word processor and the desktop has been obscured for less than a second.
Right. Winding up in front of a modern Windows computer for the first time, I was pleased to learn they'd moved things much closer to my workflow in ratpoison on Linux.