I’ve noticed some changes in jumping from MacOS 10.6.x to 10.9:
The keystroke Command Option Eject no longer puts the computer to sleep.
On the Dock, the active app indicator is much less visible. (later improved)
Scroll bars no longer have arrow buttons, so I can’t click to scroll slowly.
When I charge my telephone on USB, it’s no longer recognized as a volume. (I’ve since got an Android phone, with a tolerable interface.)