I've had OS X Mavericks for a week or so. Since Mac OS X, I've taken it a bit more slowly with my updates, upgrades.
When I went from 10.2.x to 10.3.0, things went awry. It took until 10.3.4 until most everything worked again. It seemed with every release, it took until 10.x.4 until it was stable enough for all that I did, so I waited, even though I had used the beta test versions for testing and programming purposes.
When Avie Tevanian left Apple, Mac OS X seemed to become even more sloppy. I still have a PowerBook G4 on 10.5.8 and it really could have used some bug fixes. Thankfully, they produced a number of security updates since then, and some of those helped stability.
Since 10.6.8, Apple provided (Mac) OS X on less and less media until it was only available for installation over a network connection. When I got my mid-2012 MacBook Pro, it got 10.8.0, which required updates while connected to the internet.
So, I bought a new version of Phase One's Capture One version 8. The only problem was that the software didn't work on 10.8.x and I didn't see anything about the system requirements ahead of the purchase, which seemed odd for them. Obviously, I wanted the new version of the raw development software so much that I was not thinking as well as I should have.
Having spent the money, I needed the update to OS X 10.9.x. The nearest Apple Store was okay with installing the update for me. If there was physical media, I would have installed it myself. Actually, I was expecting to occupy a corner of the Genius Bar with their internal network connected to my computer and I would install the update myself. They had a local installation image of the update and they used that.
They managed to e-mail me when they finished the update, but they didn't use the phone number they confirmed three times. Since they had my computer and I expected a phone call, I didn't check my e-mail. I returned to the store about 45 minutes before the store would close, just hoping that they had finished.
Long story, long, I've updated and my computer is still working. Mavericks is slightly better than Mountain Lion, so I feel okay about the changes. I'm not finding any interesting or odd behavior. I'm glad I did the update when I did, so that I wasn't forced to Yosemite. The only Yosemite I want close right now is the national park.
Update 2014.10.30: Some Yosemite users are reporting WiFi connectivity problems. That's a surprise! (Did your sarcasm detector max out there?) Every new release of Mac OS X in recent memory has had WiFi connectivity problems, and many iOS releases have also. Do you wonder why I wait to update?