I was also very impressed with the how quiet the tdi motor was, however after taking the top off, well thats a different story. Driving slowly (0-50km/h) such as in car parks or creeping through city traffic, side streets, taking off at traffic light, etc) the horrible sound of a diesel engine was very evident, and for a convertible it was unacceptable. Once you reach 50-60km/h, no problems, you wouldnt even know its a diesel.
As for the diesel soundtrack, ok roof on, however not a good mix with roof down at lower speeds. Its down to personal preference.
The MY09 model does not have these problems - if anything, the car is too quiet to the point people we take out in the car will not believe it is a diesel due to the lack of noise and its V8-like acceleration capabilities.
Anyone offered an MY08 version "off-the-floor" over waiting for delivery of an MY09 should keep this in mind and negotiate a bigger discount .