My argument is that in every previous version of Windows, there has been ways to revert to "classic" design elements. Win95 still included "Program Manager" for the luddites that still wanted it from their W3.1 days, XP and Vista still included the "classic" start menu. Windows 8 is the first OS from Microsoft which has implemented sweeping changes whilst simultaneously providing no official route back to the old way of doing things.
Criticism of W8 would be reduced if you could toggle the Start Menu back on, but you can't without installing something like Classic Shell. Hence I feel that it's a perfectly legitimate complaint about it.
I know that Search does still search the Control Panel, but extra steps are required to get to those hits, whereas in Windows 7 that's not required. Still a step backwards from Windows 7 IMO. New OS versions should speed actions up, not slow them down.
Not being able to snap Metro apps side by side isn't just odd, it's appallingly backwards. There's no good reason whatsoever why the desktop version shouldn't allow me to drag my PDF to one side of the screen and have Word or Firefox or something open at the other side. The fact that it's not allowed is appalling, lazy and backwards design and makes Metro apps effectively useless on a normal PC IMO.
Vista IMO was poor. The interface felt cluttered and unfinished and it felt badly designed to me. That's why we ended up with about 8 different options under "Shut down" with "Sleep" being the default option - even on Laptops, and with a hefty trip into the depths of Power Options being necessary to change it. This is the same reason that Windows 8 needs you to go into the "Charms bar", then into "Settings", then into "Power" to find the "Power off" option. It's just poor design.
Vista really needed another 6 months of development and feedback in order to correct its flaws and bad design elements. As it didn't receive that, it felt rushed and flawed to me - hence why I used it for a while, then jumped back to XP. It's also why it ended up as a flop in general. Windows 8 feels exactly the same in this respect. With a few tweaks and improvements and a bit of listening from MS, it could have been a real improvement over Windows 7. But too many aspects of it feel poorly conceived and badly designed to me. Hence, Windows 8 (to me) is a disappointment that I'll be avoiding.