After having decided it's time to part company with my SL500 I'm now deciding whether to replace it. If I do I will either go for an old w211 (I had one for six years from new and loved it ) as a runabout or move up to the w221 S-Class I've fancied for a while. I'd like to pose a few questions to those in the know.... Is the airmatic system as delicate and prone to failure as ABC? Are the running costs as extreme ( I'm looking at '07 320 CDI ) ? Have any common faults surfaced yet ? If I go for the w221 it will have to have, massage seats and 17" wheels ( for comfort ). Are there other options others would consider essential?