Uploading the MANY pictures I took on my trip to Eurofurence 27 in Hamburg last week.
Taking Flixtrain from Frankfurt West to Hamburg Central station. It only took 4-5 hours, not much slower than an ICE service of Deutsche Bahn, but for a fraction of the price. I payed just about 30 Euro both way. And those are express trains. I am sure that in some parts of the ride the speed went up to 200 km/h. Cons: The seats are narrow and not very comfortable. Also bring your own snacks and drinks, as the train does not have a restaurant car.