Yes, MIPS have made the mountain bike helmet experience much better by adding some additional feature. The most important among them is its bright yellow plastic liner inside the mountain bike helmet. First of all, it was only added in few high-end mountain bike helmets.
The idea behind the creation of this extraordinary liner was to keep you safe from the rotational force hit on your head if you hit with a foreign object or any ground at an angle. It happens because most of the crashes does not hit your head directly at straight line. MIPS solved this problem by attaching a small plastic peg with the helmet. when a strong rotational force hit on your head, then pegs rotate the helmet without whipping your neck and head.
Now, all the big brands are using MIPS technology for solving this very crucial problem of helmet safety. It is more relevant in the helmets having chin bar than open face helmets. This feature is also good for the purpose of aerodynamics because helmet easily rotates on your head without moving or resisting your body. It is also good to keep the rotational stress away from your head or neck.