Bad customer service?
No-one is going to "get over it" until it's made optional or just plain GONE. See, Apple also monkeyed with "let's put a mobile UI on our desktop OS" but they made it optional (Launchpad). It ended up being rarely used by most, but didn't bring the shitstorm on Apple. Why? Because it is OPTIONAL. As in, you're not forced to use it if you don't want to.
The Metro abomination is forced upon everyone, and 8.1's idea of "choice" means "you can choose to boot into a desktop view" but you're still forced to use the damn thing the moment you click on the "start button".
By the way, the last time a previous OS looked antiquated compared to the new one would be OSX (for Apple), Win2000/XP (for Microsoft) and the 2.6.x release of the Linux kernel for the Linux world. Arguably 7 might qualify, but even then it wasn't that much of a jump. Most posts I've seen claiming 8 makes all other OSen look prehistoric have been obvious astroturfers.