If you're a consumer, you use the Metro UI.
If you're a producer, you use the Desktop.
You can set the desktop to be default on bootup. And I'm 90% sure this is how home computers will ship from DELL. While tablets will be Metro.
The desktop is not going anywhere, MS has simply re-aligned the default UI to cater for the mass-market: the consumers that want to browser youtube, check the email, tweet, etc.
> Microsoft seems insistant on forcing users to re-learn the OS at every release.
IMO, they are insistent on improving their products.