I didn't read the whole thread but here is my opinion.
I rented a 2012 Mustang VS convertible for a few days back in 2011. I was able to fit 2 full size golf bags and pull carts in the trunk, that was surprising. I enjoyed the car, it drove relatively well. I seriously considered purchasing one back then with a manual transmission but in the end I got a used BMW convertible. If I were to buy one, I think I would try and buy a GT, but I understand that budget concerns might not allow everyone to do that. The V6 is adequate and you can get a tune that makes it even better. I would also only buy a manual.
On a side note, a colleague of mine at work is interested in selling her 2012 Mustang Convertible V6 premium. Nice car, very clean and well maintained. Always washed. She wants to move back to a small car, she came from an Toyota Echo to the Mustang, so she never felt super comfortable with with car. Let me know if you or anyone else is interested and I can put you in touch.