We took a Viking river cruise from Budapest to Prague. First the good things:
1.) The crew was great. Very helpful. They communicated with passengers and some even remembered names. I would rate the ship staff as A++++++.
2.) Budapest and Prague were fantastic. We had good weather and the cities were beautiful. The boat took a river cruise at night in Budapest and the view was spectacular.
3.) Get the silver spirits package. Worth every penny if you want a good glass of wine at dinner or a cocktail in the evening.
4.) Food was good considering the limited kitchen space available for preparation.
Now the bad:
1.) When not on shore, it is boring. There is nothing to do on the boat. As one passenger said: "my wife and I sit in the common area and play gin rummy, we could do that in our kitchen"
2.) Spend any money you receive as "shipboard credits". Any left over cannot be cashed out or used for tips. However, you are not told this at the beginning of the trip. In our case this was accrued as the result of billing errors at the time the trip was set up and frankly, I feel like I was ripped off.
3.) Prepare for spending a lot of time in locks looking at steel walls while the boat goes up. Again - boring
4.) Rooms are much smaller than equivalent on cruise lines and lots of things rattle. Our air conditioner sounded like a jet engine. In fairness, the crew did fix our problems but we often had to put up with them overnight.
I doubt we will take another river cruise.
Vienna is a fantastic city and have been there before. When to Schoenberg Palace on this trip. Beautiful and lots of opportunity to walk. Went to old town and have a latte which was one of the best ever. Love Vienna