Boxing anyone?

I hope this thread generates some posts. I am trying to understand boxing, when it occurs, why we would ever program for it to happen, and such. Here is my limited understanding of Boxing.

Boxing occurs when a value type variable is passed to a function that is expecting an object. (is there any others?)

In my app, I can only think of one reason to do this, and that is to check for a null pointer. Is there other reasons to have this?

I know that there is a resource impact with boxing, has anyone done any benchmarking on the overall impact?

With Option Strict ON, will that eliminate Boxing?

Thanks