I took an Alaskan cruise in 2001 and would do it again in a heartbeat if I only had the $$$
I went on Royal Caribbean Vision of the Seas out of Vancouver.
Enjoy the trip and if you are going in the summer take plenty of bug spray. We went in Sept when the mosquito season was over thank goodness. But you should be ok if you are going Sept 1. If they have excursions at some of the stops -- TAKE THEM. We took the train in Skagway and saw a bit of history unfold before us and in Juneau we took a catamaran out to see some of the wildlife.
Take a really good pair of binocluars. You should see some orca.
Highlight of the trip
The ship went into one of the fjords and when it went in as far as it could it literally spun around and went back out the way it came. It was pretty awesome because there was very little room for a ship that size to turn. The moveable rubbers allow it to spin practically in one spot. Truly awesome to stand there and watch the scenery shift in a circle like that.