I've had 2 four seater convertibles. Loved them both. Currently have the A4 Cabriolet.
Why did I buy it? Because it was the car that covered most bases, i.e.. the best compromise.
Some people will talk about handling and performance that is dulled by the weight. Well sure, if you're Jason Plato or Lewis Hamilton on track then it would be an issue. Day to day it makes no difference at all. Economy is a far bigger concern to me.
I've had smaller open tops too. Boxster S and VX Turbo included. Yes they're much better to drive but would spend most of the time in the garage. Work and two kids under 6 make them an expensive luxury.
So, this is my point of view... Audi A4, standard family car. Compromised rear space which is not a problem with small people but we all get to enjoy open top motoring. Personally I love it, I love it so much it can change my mood completely.
I like the looks too. The only criticism is that the A4 cab looks like a saloon that has the roof cut off whereas the 3 series cab (old and new) looks better in my eyes because it looks like a coupe that has been cut down.