No far from it ... It appears more like a layer on top of windows 7 very cheap hack indeed. Probably windows 9 will be the release that fully delivers the concept
It's not another layer on top of Windows. Read the post i linked.
The desktop UI and other parts of windows are not even loaded when using Metro. Also in the leaked Win 8 builds the code for metro is in the core of the operating system, it's not something just dumped on top. Theres new API's and frameworks for it.
Win 8 development started
before Win 7 was finished, so they've had the time to do things properly here.
In order to get Win 8 running well on far less powerful touch devices like tablets MS have made many changes and optimisations to the core of Win 8 and also got rid of much ancient legacy code. The leaked Win 8 builds for instance show all of this, you can view the code in them, and these early Win 8 builds run faster than win 7, or even XP, yet the OS is still nowhere near complete.
As for the quote:
"Essentially, you can think of the Windows desktop as just another app." ....He's only summing it for laymen here. Just calling it an "app" is easy for non-technical users to understand, but it's really nothing like an app.