My wife and I took our first river cruise of 15 days with Viking from Budapest to Amsterdam in early November 2015. Overall it was an excellent vacation and for the most part an exceptional experience on both Viking ships Embla and Aegir. That of course is another part of the story to be continued later.
I often consult Cruise Critic for trip tips prior to a vacation so hopefully some folks especially new river cruisers will find my observations helpful. So if you don't want to read the whole novelette here are the bullet points: It is an awesome trip. Go to Great Market Hall in Budapest. See a concert in Vienna and get a chocolate torte. Passau is best city to shop. Go on the Nuremburg, Rothenburg, and Pub Crawl in Cologne tours. All of these are special Viking offerings that are not included as free excursions. Make sure you are on the upper (sun) deck when sailing through the Wachua and Rhine valleys. For Ocean cruisers there are hurricanes. For river cruisers there are high water, low water or broken locks. Although it will be well handled, your trip could easily become a land tour. No, you don't need a balcony.
Itinerary tips:
Fishermen's Bastion for beautiful views...
Highlight is artwork man exiting manhole.
Stephansplaz is only a 4 stop subway ride from port.
Buy the honey liquor in the gift shop.
Best city to shop.
Try sausages at Sausage Kitchen below the stone bridge.
Unfortunately needed more time. Documentation Center should be a required visit for everyone.
Walked around city on our own. St.Martin's celebration with parade and bonfire was very cool. Like a second line march in NOLA.
Good to gain experience with the city. Very diverse.
Impressive Cathedral.
Pub Crawl was awesome.