Last September/October, 2002, I was among a group of 32 on Viking's Grand European, a 16-day/14-night river cruise from Amsterdam to Budapest. Last month, May, 2003, I arranged for another 16 cruisers to do the same itinerary. There was not a single complaint from anyone! Everyone raved about their first river cruise experience, many declaring that it was their favorite cruise experience ever and announcing that they may stick to river cruising from now on, rather than ocean cruising. Viking's food is excellent and beautifully presented. The tours are outstanding--conducted only in English by personable, knowledgeable guides. And best of all, they are included in the price of the cruise. Peter Deilman's excursions are optional and not included in the cruisefare. While Viking markets to United States cruising
Most of the members of these groups have sailed on Renaissance. Some, like me, have sailed on Ren multiple times. It was, in fact, our favorite cruiseline. While river cruising is quite a different experience from ocean cruising, there are definitely similarities between Viking and Renaissance: ambience, friendliness of the passengers, a crew dedicated to making the cruise a positive experience, open seating in the dining room, very limited smoking areas, no children, and "country club casual" attire, with no formal nights. Peter Deilmann for sure, and I think on Uniworld, too, there are formal nights; on Viking men do not have to wear ties or jackets, though they are suggested for the Captain's Dinner (about 30% seem to adhere to the suggestion).
In addition, river cruise boats--even more often than Ren--can dock within walking distance of the city center. Never is a tender used! On a river cruise, you get to see quaint towns and magnificent cathedrals, and lovely scenery "up close and personal" right from your stateroom, just about 24 hours a day.
When it comes to fares, Peter Deilmann cruises are definitely in the high-end bracket. Uniworld and Viking are probably quite competitive, each offering excellent promotions from time to time. At this time, Viking is offering a savings of $900 per stateroom for selected sailings of the Amsterdam/Budapest itinerary.
I hope this helps you with your decision.