When booting up my Macbook Air, when you see the Apple logo and after that the login screen, the animation that goes from Apple logo to login screen is very jerky. I'm running Mavericks now, it used to be very smooth in Mountain Lion...
Yes, Mavericks is still unrefined in certain areas. They improved a lot of the functionality, but the small things that make OS X such a pleasure to use are rather glitchy at this point.