I think he talks about something else. When I installed Win8, and then cygwin, and all other tools that I use - then the Metro screen became full with lots of icons that you can't read the whole names easily, and all of them were the same. I don't even see some of these names in the Start Menu (or maybe i did not check, because I don't go for example to the menu for them).

So the problem is that it flattens out the whole tree structure, and while I think this is good idea (I like the OSX dock), it's good idea only if you have few important things there. If it's get too cluttered easily, then it's not.