Just came back from a business trip to Aachen. Flew to Frankfurt and took the train to Aachen, changing in Koln. The experience was pretty much as bad, if not worse, than what we see in the Northeast US rail corridor. Watching the board at Frankfurt Flug station, nearly every train was late. We had a tight 12 minute connection at Koln Hbf (normally plenty), and arrived 18 minutes late. Fortunately(?), that train was 20 minutes late...as were most of the trains I saw on the board.
Coming back yesterday was even worse. No issues Aachen to Koln, but trains in Koln were being cancelled left and right...at least half. All of the trains that were running were 30-45 late. Fortunately I hit the DB info booth, and discovered that the Munchen Hbf train was being rerouted to hit FRA Flug. The train board, and the info screens on the platform did not show this info. When the train arrived, no conductors got out of the train, so I had nobody to ask. I stuck my head inside and saw the car monitor, which showed Frankfurt Flug. Had I not known to do that, and there were tons of confused passengers milling about the platform--German and visitors--I would have missed the train. Standing in line at the DB info booth was the best decision I made.
Don't know if there was a maintenance shift going on, or whether there was a one-time issue. Nobody seemed to know. Just wanted to relay my experience to those who might be traveling in that area and are assuming that the German rail system is this perfect entity. It's not. Give yourself time, and don't be afraid to ask questions.