Viking river cruises are unique for a number of reasons. Firstly, there's the shape of the boats in the Viking river cruises fleet. They are substantially lower and flatter than modern cruise ships.
This allows the ship to get under very low bridges, which in turn will allow the low ships to get to place that no other cruise boat can ever reach. This give Viking river cruises a unique advantage over its competitors in its ability to get its passengers so far up the river. Viking's fleet of river vessels are the world's biggest so you know when you go on a cruise with Viking river cruises that you're sailing with the world leader in its class.
Another big benefit is the flat bottomed nature of the big but low boats. This allows them to cruise on Scandinavian rivers without causing anyone to feel sea sick. This is great for people who get sea sick but have been unable to find somewhere to cruise where they won't get sea sick. Viking river cruises is that place, so they should take to Scandinavia as soon as possible.
Now, though these ships are built for the rivers of Europe, China, and Russia you shouldn't expect anything except the very best in terms of service. It's still a cruise ship so you should expect luxury service. The ship are of Scandinavian design, and the customer service quality is very high.
For those of people who go for a state-room, they're lucky because all state room have huge windows or a balcony from which to enjoy the scenery. River cruises, especially those with Viking river cruises, are especially good for those people who want to look at the scenery. Unlike on cruise ships where you will often go for many hours or even days with nothing but water to see, river cruises guarantee that there will always be something to look, marvel at, and photograph.
The menu on the Viking ships was created by both European and celebrity chefs which ensures that there is apparently a gourmet aspect to the cruise. As the world's most award winning river cruise line you can also be sure that when they make these sort of claims that they can be backed up with facts. So for the traveller who wants to see Paris or Cairo on a cruise ship but never thought it possible, there is in fact a way, and it'll often work out cheaper than an ocean cruise.