Quite interesting that Joopson.

What are the setting that you used with MR?

edit - Just saw the specs that you had.

I think that the large MR times might be that you have everything on, which you dont really need. I think that MR would be faster when the render's optimised, also what happens when the geo's upped to have more materials etc? That would be good to see.

As I said it would be interesting to see what results you get further down the line.