This is a truly remarkable part of the voyage for mountain scenery. The sight of the Lyngen Alps with the sun descending like a huge red ball is not something you will forget.
In Tromso, you may find that a trip to the funicular on an ordinary bus is better value than the official excursion to the Arctic Cathedral and other stops. Note that the Arctic Cathedral is not actually made of ice -- it is a striking modernist church with a distinctive triangular facade.