I would never slate the 335d as it is an awesome car (no doubt many people will think I am crazy going for the S3 after a 335d). My wife has the same engine (remapped of course) in her X5 3.0sd and that surprises many people!!
Regarding the interiors I personally think the quality of BMW and Audi are on a par, I certainly liked my 335's.
I had the 335d for nearly 3 years and after owning 2 x S3's in the past I fancied trying the new one with Stronic for a change of car style.
Fair comment Nick and you have a balanced opinion.
I just drive home from the office for lunch in the S3 then back in the 335d and will say again it is so hard to compare such different cars but on the same stretch of road the 335d just has the edge, to be honest both are ridiculously fast for road use, good fun though