Flatter but not iOS 7 flat and with more transparency.
As someone who used Windows 7 I am not a huge fan of the wide use of transparency. Fortunately, this appears to be more understated than the “filmed in Glaucomavision” of Windows 7. Also, unlike our iOS 7 complaints last year, the icons in Yosemite look terrific.
So much to dig into here from things that were fixed (Airdrop between OS X and iOS) to things that are new (connected states with iOS devices). Apple’s platform is taking it up a notch.