Hey Rob. Been using and testing win8 for quite a while @ my company and pretty much agree with all your points.
However for your section
"Start Screen: Killing Modern UI apps is unintuitive"
The fastest way to kill a metro app is to bring your mouse to the very top, a hand will appear and then drag it down to the very bottom.
To view what apps may still be running you can point to the top left while on desktop, right click and close them as well. Or you can also use the snap as you mentioned.
But yeah the main issue is that I did not know these from the get go which is a failure on MS' part in making things intuitive.