For me there are no showstoppers, though. I'd go as far as saying that I slightly prefer using 8.1 + Classic Shell (with filetype associations re-assigned to non-Metro applications) to a stock Windows 7 installation. Startup is quicker, the file copy dialogue and task manager are improved, and I never liked Aero Glass. There's certainly no compelling reason to 'downgrade' to Windows 7, any more than there is to 'upgrade' a Windows 7 system to 8. Of course, if I were stuck with a locked down Windows 8 installation with its horrible default configuration and jarring interface shifts, that would be an entirely different story. Windows 8.x is still an awful experience out of the box, but there's nothing serious that a knowledgeable user with an admin account can't fix in 10 minutes (or at least, nothing that has affected me so far).
Pretty much this. The worst part of Windows 8, out of the box, is the interface shifts for tasks such as looking at image files. But fixing those is pretty easy. When the lousy "Photos" app opens, close it, right click the file, "Open with...", and change the associated app for all files of that type. Do it once and never think about it again. I can't remember the last time I was shunted into Metro.
If you don't like the start screen, install Classic Shell or Start8. (I actually prefer the start screen, but due to a multi-monitor issue--well, Eyefinity issue--I'm now running Start8.)
What I like is the number of suggestions to "just install Linux", as if Linux needs less configuration than the above. I think people who make that suggestion are ignorant, biased, or would always recommend Linux simply because it's their preference. The last one is fine in certain circumstances, but those people should be honest about it.