A lot of Unity's Structs' operators can have a massive performance increase, in a very simple way.
In my test script (available here https://dropb.in/ponda.nimrod), I reduce the Vector3 multiplication cost from 18.9 ms to 2.5 ms
If we take the * operator as an example, the current implementation does this:
return new Vector3(a.x * d, a.y * d, a.z * d);
The implementation I suggest would be like this:
result.x = a.x * d;
result.y = a.y * d;
result.z = a.z * d;
This avoids calling unnecessarily the Vector3 constructor.
What I just explained for the Vector3 struct it is also true for other Unity's structs (like Vector2)