Years ago German trains were dependable and efficient. Now, according to my German friends, they have deteriorated so badly that Spanish trains run on time more often. I'm back from a trip to Germany, and I sadly concur. I took a round-trip ICE train from Berlin to Hannover and back, plus an eight-hour ICE train from Berlin to Vienna. Here are my takeaways:
The Berlin-Vienna train was late even leaving the main Berlin station. By the time we got to Vienna, it was 40 minutes late. We had a concert to see that evening and had to scramble to get to our lodgings, dump off the luggage, and make it to the concert hall in time. My advice: Don't count on on-time arrival; build in extra time in your travel plans.
None of the ICE trains I took had power outlets. If you didn't charge your phone/tablet/laptop before you boarded, you were out of luck. I traveled first class and was astonished by the lack of power outlets. I walked up and down the train to see if I could find any--no such luck. My German friends said that some ICE trains do have them, but the three trains I took didn't. My advice: Don't count on power and bring a smartphone battery backup.
On the Berlin-Vienna train we didn't bring our own food because we looked online and saw the Deutsche Bahn ICE menu. It promised a variety of yummy offerings. Also, in first class, the staff "will take your order and bring you your meal." Ha ha, we were really burned by this. No one ever showed up to take our order. I went to the restaurant car and found that the offerings were three kinds of pre-made wraps/sandwiches or a bowl of chili--that was it. My advice: Don't count on the food service, bring your own instead.
I encourage everyone to take trains in Europe. I guess I've been spoiled by TGV in France, AVE in Spain, or Thalys (now Eurostar) trains from Amsterdam to Paris. It's shocking that the trains on Deutsche Bahn are inferior to these systems. Be prepared--German trains aren't what they used to be.