[Xylakant]

It's not 'a few slow or cancelled S-Bahn'. Last winter season the system was so strained that the S-Bahn to the airport was running only every 20 minutes and was pretty much guaranteed to be either late or cancelled. So to get in time for your flight you had to leave like an hour earlier than planned. It's slowly getting better, but the last couple of winters you pretty much could not rely on the S-Bahn if you wanted to be anywhere on a specific time.

Compare it to Munich, where it's a minor scandal if one S-Bahn is like 5 minutes late. That's outstanding.

[redbad]

"Every 20 minutes" for an S-bahn is totally fine! Especially compared to cities like New York, where every 20 minutes for some U-bahn equivalents would be considered good.

[Xylakant]

Every 20 minutes on one of the main lines is not fine. Even if it were fine, it's only fine if you can actually rely on the schedule, but not if you need to take into account a high chance that it's '1 hour wait and then three trains in direct succession.' Slow, but reliable service is ok. Slow and unreliable is not.