Micheal, why not go to a dealer and have a drive, some of them will rent you a car so you could go for a weekend.
Suffice to say morgan driving is different to most other cars, but I did nearly 25k miles in my old 1988 4/4 in my first year with it, including a trip 4 up to spain and south of france. I haven't lost any fillings yet or developed a spinal compression injury. In fact I would go as far as to say it was comfortable, it is however noisy.
My car is not fast in the porsche sense of the word, but it is a huge amount of fun at relatively low speeds. I would imagine the plus 4's and roadsters are properly brisk as 150hp in a 900kg car should provide lots of fun, I don't think mine even has 100hp these days
