I'd like to say how it all looks from my perspective.
I'm pretty new to Apple ecosystem. My first Mac is 13" Late 2013 rMBP which came preinstalled with Mavericks. My earlier experience with Macs was with Mountain Lion, but just from time to time on friend's iMac.
I really liked the design of Mountain Lion it wasn't all candy, it wasn't all brushed metal. It was balanced and inobtrusive. I really enjoyed Calendar, Notes and all other apps' specific design. Notification Center and Mission Control had nice-looking "skin".
When I first turned on Mavericks, it felt like OS X slightly brushed Windows and some of its paint has come off. It has lost a lot of stuff that was characteristic to OS X. It felt boring and hollow. It wasn't that bad though- somebody might say: "OS X turns 18 and has to be serious now". Fine.
How do I feel about OS X Yosemite? I have very, very mixed feelings. Maybe not necessarily about design language, which feels half-baked to me, but about care for details.
In my opinion complete design overhaul (literally everything visible to user) is not possible in less than a year, even for such a huge company as Apple. They should have given it more time to avoid bugs and reconsider everything one more time.
As we speak I am facing several bugs concerning OS X 10.10:
- WiFi issues have started 1-2 weeks after updating.
- Phone calls on Mac have stopped to work in the same time ("Your phone and Mac need to be on the same WiFi").
- TimeMachine is crawling with bugs. I can switch between backups smoothly only from the root and then I have to go up.
- MAJOR graphical glitches all across TimeMachine.
- Mail corrupts sent and received .pdf files.
- Finder displays or not catalogue contents based on width of sidebar (sic!).
- Inconsistency (White mode top menu bar drops shadow as opposed to dark version).
- A lot of graphical insonsistency all accross OS. "Skeuomorphism" wasn't dropped - it's still used but with flatter icons.
- With many inactive windows on top of each other, you can't really say what is what.
When I'm sitting here now I recall how I was upset about one slight issue with Mavericks 10.9 (first iteration). Contact pictures used to get misaligned (show half of face for example) after syncing with iCloud.
Oh, my issues then and now.