Wow this guy really misses the skeumorphic interface and really doesn't like minimalist design. Sheesh.
Personally I think OS X has been improving as its gone minimal. I don't like skeumorphic apps. They seem at first glance like they are easier to use, but the analogy actually many times makes they interfaces more misleading for novice users when they can't do everything that they expect they should be able to.
The Finder side bar is a perfect example, for me, on how minimizing an interface can make it more clear. The old Finder side bar looks cluttered and noisy and it can be hard to easily understand everything that's going on there. The more minimal one is easier to read. Could it be improved at this point by bringing some color back? Probably. But sometimes you have to go "too far" minimal to then find where you can bring things back in a way that really improves things.
The OS X interface was in dire need of a reset like this. If you ask me the main problem with the OS X move towards minimalism is that it's been too slow and didn't go far enough in some areas. I would have preferred that OS X went all the way right off the bat and then we could have already been on the path to bringing some more color and shading back in that will probably happen over the next several years.
At least, though, I agree with the author that the Game Center icon is awful.