Learning differences between ByVal and ByRef

I am trying to learn the differences between ByVal and ByRef. Below is a summary of what I have currently learned (or think I have ):

1. Change original variable passed as argument: ByVal = can not change (passes a copy of the value only), ByRef = can change (passes the original reference) (hence their names)
2. Passing Arrays: ByVal = Can't do (error), ByRef = Always use for passing arrays as arguments
3. Passing objects: ByVal = Can not use on objects? ByRef = Always?
4. Speed: ByVal = slightly slower, ByRef = slightly faster
5. Argument type: ByRef = must be same variable type passed? ByVal = ?
6. If not declared: ByVal = not default, ByRef = Default

My questions:

1. If there is anything I have incorrect in the above, could someone please let me know?
2. Is there anything important missing from my summary that I should be learning?
3. I fail to see any benefits of using ByVal over ByRef (unless you are paranoid about the possibility of altering the original variable). Or am I missing something big here? Please enlighten me if so.

Thanks for any help/corrections.