Visibility in the cabrio is substantially reduced (the rear window is smaller than the coupe's) ... especially reduced in stage two open. In both models, a good third of the rear view mirror shows seat back rather than a view behind your car. I find that I readjust the rear view mirror and rely more heavily on the side mirrors when I've got the top back. I also have a rear view camera.
Discoloration on the interior side of the roof may be coming from contact with the roll bar according to some discussion on this forum. Mine show some of this and I am being more diligent now to keep my roll bar clean. For me, at least, the question of how to clean the interior surface is my primary cabrio concern.
I generally keep the windows closed when the roof is back. Just a bit too much air for my taste with the windows also open.
I haven't heard of anyone having problems with the mechanism. I am hoping it is very durable because I use it frequently.
I absolutely love my cabrio and have the roof back whenever practical. Nice that it can be opened and closed at any speed. I don't regret getting the cabrio at ALL.
Oh, BTW, I've recently discovered visibility can be tremendously improved when you're not carrying a passenger simply by folding the passenger seat down. That should hold true for either model. And, it makes a decent arm rest too.