I just sat in one the other day V6. The dealer had about 5 cars, no EBs though, and every one had a sign "Unfortunately test drives are not yet available for the 2015 Mustang."
I found the mirrors very small and the blindspot section too small to really give you any perspective (it's a bit bigger than a quarter). But, I did not use them in a dynamic situation since unfortunately test drives were not yet available for the 2015 Mustang at that dealership.