I have a 1992 Four seat 4/4. My father (hello!) bought it new, and growing up I have spent many an hour sitting in the back. As a tall 16 year old, the legroom was a bit of a challenge, especially with the roof up. With the roof down, it was much easier to get into the rear seats, but in that model of car, as a rear passenger you looked over the windscreen, thus it was important to keep below 40mph.
Since I bought it (in 1997ish) I have noticed that having a couple of adults in the back (it can be done) **really** changes the handling of the car. There is much more roll on corners, with the rear wanting to hang out in a very disturbing manner.
Acceleration was also noticeably affected.
The rear seats do provide plenty of space for shopping / bags. I'd recommend a full tonneau cover, as this provides excellent concealment of belongings when the roof is down. I sorry, I have no experience of modern four seaters.
