You still had to open the start menu to launch things...so you had to switch away from the current task to launch the new one.
The old start menu used a folder hieracrchy that required digging through levels of folders sometimes to get to the actual program. The new start screen gives a 'flat' approach to the hierarchy which means less digging.
I think what has people upset is purely the fact that it's a change. Instead of a small menu on the bottom left it's a full-screen menu. Functionally it's not really different...aesthetically it is.
No, with the old Start Menu you never lost sight of the entire desktop and whatever was going on it. Everything stayed in front of you. Like the current Start Page, you just type the name of the app and click on it, again, never losing sight of the desktop or having to scroll or survey more than the well defined area of the Start menu to find the result and click on it. Definitely didn't have to click Apps/Files/or Settings.
I'm not saying Metro isn't workable, but the notion that the Windows 7 Start Menu was inefficient or that the Start Page is more efficient is a stretch IMO. So many things are "more" work, whether click, draggin' selectin' or eyeball movin'. Metro works on the desktop but wasn't made for the desktop and we all know that.