We just returned from our Alaskan cruise that sailed on May 31, 2006 from Vancouver, Northbound for Alaska.
Our family consists of myself and husband (early 40s), sons (18 & 21), my parents (65 yrs old). My family has been on 6 cruises. Three with Disney, three with Carnival. This was my parents' first cruise.
We really enjoyed the Northbound itinerary because the scenery gets better as you travel North. I completely agree with previous reviewers - you need a balcony to really appreciate Alaska. I would suggest a room with a 60 square foot balcony if you plan on spending a lot of time outside. Unlike the Caribbean where all you see is water, there is scenery most of the time. We were able to see whales swimming beside the ship many times. Also saw a bear with cub, sea otters, and bald eagles.