I am willing to pay for a true luxury experience and that is what I thought I would get with Viking River but this is definitely not luxury, maybe 4 star for accommodations and 3.5 for food. Using an analogy to hotels, let's say Four Seasons/Mandarin Oriental/Conrad/Montage, etc. are at a top level 5 (which Viking River most certainly is not), Viking River is akin to a good Hilton. I splurged, I really wanted the luxury experience. So I paid extra for the verandah suite. Accommodations were nice especially for a "cruise". Spacious, clean and modern facilities (including a walk in shower with heated floors, an appreciated touch during the cold German nights).
HOWEVER the food and service is definitely not luxury. Breakfast/lunch/dinner items are extremely generic and usually bland (to accommodate the tastes of the elderly who frequent these cruises). I ended up skipping dinner altogether most times and just having a protein drink in my room. For fitness buffs like myself, there is no gym by the way on these small river cruise ships which was a complete bummer.
Similarly, the SERVICE was not luxury. The wait-staff are salt of the earth nice people who do a good job, but the level of deference and "invisible" service that you get at true luxury properties are not found here. Instead it seems the staff, particularly in the restaurant, are instructed to be outgoing and garrulous which is tiresome for me on a trip that is supposed to be relaxing.
DO NOT GO PAY FOR OPTIONAL EXCURSIONS. My huge mistake they are a complete ripoff and the guides are extremely hit or miss. Not worth it in the slightest. I paid $279 for a trip to Munich, it was literally just a drive there and back, a walk around town and a gross pre-set lunch already pre-negotiated with a restaurant specializing in mass tourists.
World War II short optional excursion was okay, just went to a few places and all of them were FREE to go to so not really worth it.