I take issue with most of this article. The things that the author got right:

• There are three shapes that Apple are using for icons
• Titled 3D icons are orthographic
• Subtle color additions to metal materials

Everything else pretty much misses the mark.

Edit

I am probably being too harsh. I had a strong negative reaction to overlaying the iOS icon grid over the icons, some of his supposition and opinions, and that crazy jumping hover state on the metal icons illustration.

What I find misses the mark:

• Applying the iOS grid here just doesn't work, and the author's grid doesn't look right to my eyes either. (Note: I didn't work on App Icons for Yosemite)

• I wouldn't take the authors recommendations on using a particular genre for a particular type of app. For example, I wouldn't use a circle for a to-do list app per his suggestion (and in fact Apple use the titled icon style for Reminders).

• Also, Ambient Occlusion refers to the level of exposure that a particular point has in a scene, not it's color. Ambient Lighting or Global Illumination is the correct term.

• Ugh, that hover.

Nice article! I'm a big fan of some of the new icons (e.g. the new settings icon: Really well done, imho). It seems like Apple has heavily used 3d programs on icons for the first time (good to see at the Text Edit icon, which seems to be a bit too 3d'ish, realistic). But I'm a bit sceptical about the sense of their icon grid, as mentioned in the article … It's a bit ridiculous to force it on each and every icon. And the author seems not to understand what “ambient occlusion” explicitly does in 3d. Just as a rough subtitle under an image with spheres doesn't really make sense. AO is more about “dirty” corners than colored bouncing light. Maybe he meant global illumination (GI)? All in all I think it's really great to see that there are still some good icon designers at Apple, after the iOS7 icon shock …

Apple really hit a home run with these new icons.