You know me, I updated within a couple hours of it being available. I do have good, multiple backups, though.
Absolutely no problems whatsoever. The look is quite weird, but like so many visual changes before, we'll get used to it. iTunes finally got rid of the sidebar, which has been coming for a while. I wish they hadn't...
Oh, and mdflagwriter doesn't grow any more. After 24hours plus, it is just 1.2 MB. On Mavericks, it would have been 500 MB or more by now. WeatherCat seems to be using about 100 MB more than under Mavericks, though. All in all, having all the same applications running that I always do, I have a lot more free RAM than I did.
Steve