How big of a factor do you exige owners think having no back window is?
1. It's not a problem while driving. I use multivex mirrors to increase my side-viewing angles.
2. It's a freaking pain when backing up: you have to constantly scan between the left and right mirrors to see if anything is approaching you from the side you are not currently looking at.
Even with a backup camera, it takes me about 10x longer to backup out of my parking spot in the Exige than it does in a regular car.