We have cruised on 4 different cruise lines. This was our first time on Viking. In comparison to other cruise lines, Viking is elegant, subdued, classic, and very grown-up. This goes beyond the fact there were no children on board. Every time I strolled through the ship, there was a beautiful violin/cello duet playing. The onboard seminars were as educational as a college class.
There was something like 500 crew members to 850 passengers, so there was always someone close at hand if you needed anything.
The food was great. The excursions were great, though sometimes not exactly what was advertised. For example, we signed up for an "all day Railway journey," and spent half of the day on a bus. Still fun, but not what we expected.