"Auto-lock" on scrolling and sliding when using touch-pad. Now you have to click and hold down and move to the sides, to not zoom when you are moving/sliding to the sides. Once you have noticed it irritates you a lot! And zooming/sliding is probably the feature that is used the most.
Just notice when you are using your finger on a webpage on iPhone where it is also possible to move to the sides. If you start to move down, it will lock to moving the page up/down. If you start by moving diagonally the lock is not activated.