We chose Viking because of their excellent customer service. This cruise line pays attention to details. One memorable detail is them meeting us as we boarded after the Russian cultural dancers evening with hot chocolate/Baileys Irish Creme. We were also given the opportunity to experience extra dinners in the specialty restaurant, as they were available. Our cabin steward was friendly, and kept our cabin cleaned and stocked.
All of the different ports of call were interesting, and the included tours were informative. We also enjoyed several optional tours along the way. One of our ports was a small town Eidfjord, Norway, accessible by our smaller ship (many of the other major cruise line ships would have been too large to port there). Our post-trip days in Iceland were really fun and interesting, as well.
The entertainment on board was very good, especially the magician and the atrium string quartet.