I upgraded to Mavericks from latest ML. The process was very smooth, nothing broken when new system opened up. So far I only found ibooks seemed to be very buggy. Some books flied out of screen upon opening, by which I mean I could see the book by expose and right-click-menu but not on a normal screen. Some books synced well, while others not. Sack of pain. Totally unreliable before next update, I think. Is it just me???