Since I've upgraded from 5.1 to 5.2 my mecanim transitions don't work properly at all. I have a 2d character with limbs moving about the z-axis. In 5.2, the transitions aren't smooth. The limbs twitch here and there, sometimes jumping to a completely new angles. I've loaded a 5.1 build into 5.2 and a 5.2 build into 5.1 to confirm that identical projects behave differently in different versions of Unity. I think it may have something to do with how it transitions larger angles greater than 180 degrees. It seems as if the angle is less than 180, it makes a smooth transition but if it's over 180, there is a quirky "jump" in the transition.