I currently have two Macs. A late 2013 rMBP 13" which works flawlessly, and an iMac 27" with 680mx(later 2012?).
The iMac has felt wonky for lack of a better word. It doesn't hang or crash more than Mavericks did, but f.lux causes WindowServer to crash randomly which makes all users to be logged out in a microsecond. I've reported this of course.
Another thing that troubles me is the amount of rubbish logging done by the system. Have Console.app open for a while and see what nonsense it barfs out. How can it work at all with all those problems?
I had a lot of WindowServer crashes with my 30" external monitor at work when I upgraded to Yosemite. Found huge discussion threads on it on Apple's forums - it's been fixed in 10.10.2, so if you get on the beta channel for updates that should hopefully solve it for you. It fixed it for me and the latest beta seems solid. It was happening to me every time I unlocked my computer, and I would lose all my windows/tabs - maddening.
that model of rmbp has flickering keyboard light issue. if you set your display and keyboard brightness to about 2 bars, in a very dark room keyboard will flicker.
The iMac has felt wonky for lack of a better word. It doesn't hang or crash more than Mavericks did, but f.lux causes WindowServer to crash randomly which makes all users to be logged out in a microsecond. I've reported this of course.
Another thing that troubles me is the amount of rubbish logging done by the system. Have Console.app open for a while and see what nonsense it barfs out. How can it work at all with all those problems?