In my brief look at it (I haven't used it, just looking at screenshots) it looks like there is going to be a lot of moving the mouse if you want to use the mouse for the start menu still. I have gotten to where I don't even use the mouse on the Windows 7 start menu though so that's no big deal for me. Heck, I don't even use the quick launch icons on the taskbar anymore. It's more efficient to hit the Windows key on the keyboard, type two or three letters and hit enter. But for those who need to point and click, it will still seem like a bad deal compared to Windows 7 I'm guessing.

I have heard some people say Windows 10 previews are faster than Windows 7 on the same hardware.

I'm still not sure what the big problem is with Windows 8. If you don't use the mouse (which someone who cares about being productive should really learn not to do) Windows 8 is just another way to manipulate files and programs. If you're mousebound though, I can see the problem. Also, I haven't actually used  Windows 8 more than borrowing my Dad's laptop for a few hours to learn about it. I did not like it during that time period, but I mostly chalked it up to not being used to it.