I took the S3 to my local dealer (Lincoln..) the warranty chap took a few details, photos and off he went. Had a phone call two weeks later from the bodyshop saying it's ready to be booked in. Off it went for the week. (8p 1.6 A3 courtesy car..
).. came back and after the initial "OMFG WHAT HAVE YOU DONE TO MY PAINTWORK" (they valeted it...) they'd done a great job of 'the' areas in question.
The reason I say 'the' areas, is, the lower doors, tailgate (and somewhere else, I forget now..) weren't done! Only the roofrails.. Not their problem, they were a third-party shop that Audi used.. I was advised to take it back to Audi.
Upon doing so, the warranty man said that the roof was the only area that was quoted for.. A little hard to understand, as, when I first when around the car with him, I pointed all all areas that I knew of. (and he photographed them..) SO, it was a case of having to take the car back for the rest of the work! Nightmare.
SO. It's definately worth doing but A) Make sure they're happy about all of the areas you point out. and B) DO NOT let the bodyshop 'valet' the car.. PITA.
But yes, as James states, it's a 12 year warranty
!
Hope this helps.