I just got back from a January cruise on the Sir Richard With with my partner. Winter is a fantastic time of year if you enjoy the snow because the views are breathtaking and there are no crowds at all! The ship was only at about 1/6 of its capacity and all the sites along the way were clear of crowds. Of course, the Northern lights were very special; saw them 3 time despite cloudy conditions through most of the artic circle. But by far the best thing about the Sir Richard with was 2 hot tubs on the back of the deck, which you could soak in the breathtaking views in comfort and style. Only complaint there is the the ship's railing were are eye level while in the tub, wish they though of that when they installed it!
The ports have a fabulous opportunity to explore numerous towns and cities. The ship had a tourism desk that was a wonderful idea but poorly executed. They only had maps for 2 of the 11 ports we got off the ship, even though each of the town's tourist offices usually produces one. So make sure you research the port cities in advance. The internet on the ship is mind numbingly slow. The excursions sounded fun but we were more than happy to explore the towns on our own.
Instead of booking the full trip, we booked 2 parts: Bergen to Tromsø (4.5 days) then stayed in Tromsø and caught the same ship as it returned south. To me, this was ideal as it provided a much needed break from the ship to go snowshoeing around the beautiful Tromsø area.
In Tromsø, my partner and I stay at an absolutely gorgeous cabin with a fabulous Norwegian host family living across the street. They were ready to loan us snow shoes, skis, their car, even came to knock on our door when the Northern lights were out! Can't recommend them enough: http://www.holemarkgaard.no
Lastly, for those that our interested in environmental impact, we learned from the ship's manager that it did dump its "grey water" waste out at sea as soon as they were far enough off shore. This surprised me because the WWF site had said Hurtigruten did not engage in this practice, but there you go.