Just a nitpick: What features were lost in the transition from the start menu to the start screen? The start menu closes if it loses focus anyway, so you can't do other stuff with it open. Arguably, the start menu not being full-screen is a bug. I suspect this is just a case of people not liking change, no matter how trivial.
Well, it did lose the off button, but other than that I can't come up with anything.
> Arguably, the start menu not being full-screen is a bug.
A bug introduced in Windows 95 that they waited until 2013 to patch? I think after a certain number of years it might have moved from a bug to a feature.
For me, the problem with the new start screen is exactly what you describe. I'm fairly scatterbrained. When I'm going to open a program, file, etc., it's usually because of something else I have open, like an email with a request from a co-worker. When the start screen takes up the whole screen, I get distracted from the reason I opened it in the first place and have to go back to my email before I remember. I know that it's my problem, not Microsoft's, but at least having the choice between overlay or full screen would be nice.
I consider the context-switching of the huge fullscreen start menu the same as the "forget why you entered a room when you walk through a door" phenomenom.
Well, it did lose the off button, but other than that I can't come up with anything.