If that was the S1, it's awful at the moment. Supposed to run every 20 minutes and yet frequently 10-15 minutes late. If I need to use it I generally aim to get the one at least one before the one I _need_ to get, because it's just not reliable.

That’s interesting. I have a vivid recollection of a collective outrage from passengers on the platform at Gelsenkirchen when a train was running 3 minutes late.

Yep. Just what you want from an airport train, massive uncertainty.