It seems that the only people who click the start button are people who don't use Windows all the time. Commonly used apps go in the launch bar and infrequently launched apps are found by hitting the Windows key and typing the name. Nothing in Windows 8 changes that workflow for me.
I think your theory is wrong. Specifically, I use Windows for work all the time (due to Visual Studio) and I never do the typing thing. I can't even remember the name of the applications I don't use often, but I remember the icon so that's what I look for. I really don't think I'm alone with that.
If you don't use the application often, then you're probably not hunting for it in the Start Menu often and thus not going to be wasting your time in the new Start Screen often. For the very few times you do need to find the application, I'm sure the Start Screen will make whatever you're looking for discoverable.
