I went on one of the Inside Passage cruises at the end of last summer. I would highly recommend it. It was one of the best vacations I've ever been on.
It left out of Vancouver. We got there a day early though and went killer whale watching. That was probably the highlight of the trip for me, but I had fun the entire time. The next day the ship left and sailed first for three days to Hubbard Glacier at the top of the passage. We got real close to the glacier and got to see a bunch of calving and tons of wildlife and everything. Then the next day we made our first stop at Skagway, then the next day at Juneau, and finally at Ketchikan. There were tons of different excursions to choose from at each port. We went dog sledding, took a helicopter to the top of a glacier, and went halibut and salmon fishing. We all loved the trip, and like I said, I'd highly recommend it.
I also made a thread in the photo lounge a while back with some pictures that I'll try to find. If you have any more questions let me know; I might be able to answer some.
edit: Here is the link to the photos from whale watching and Hubbard Glacier...