For my 65th we wanted a grand trip, so we chose the 14 day cruise from Amsterdam to Budapest with an extension to Prague. The Viking Cruise was quite good but ultimately somewhat disappointing.
The main issue was due to a problem with the locks. We ended up spending more time on buses, driving to places in South Germany and then sailing past those places the second time than was planned. Particularly disappointing, we lost one of our two scheduled days in Vienna -- which was the whole reason I had selected this particular itinerary. That said, Viking did a great job of responding to something that was not in their control. We literally swapped ships. And the cruise director Caitlin was amazing and completely professional in how she handled everything. She made lemonade out of lemons and salvaged what could have been a really disastrous situation. True grace under pressure there.
In hindsight, we should have done the one week cruise from Regensburg to Budapest and added on time in Vienna and Budapest as well as Prague. The Prague extension was wonderful and they did a great job on that part of the trip (other than the lunch at the truck stop in Brno, which left a lot to be desired.). One day is just not adequate for a great city like Vienna, Budapest or Prague. And one day was all we had in Vienna and Budapest due to the lock problems.
Extremely comfortable and well thought out. Quite spacious for a cruise.