I definitely feel bad to those with leaky roofs, but like foosh says, this is clearly a small minority. I wish BMW would find a fix for the few that leak. If you think about it, it doesn't make sense that this would be incurable. It would be like a plumber coming to fix your leaky sink and saying "Sorry, there is just no fix for this one.". I mean WTF? I think it must be damaged seals like I had said earlier. Either that or a manufacturing defect somewhere in a certain batch of cars.
I also wonder, do 3 series convertible owners complain of the same thing?