Sitka is a fine port. The excursions offered are not as many as Skagway. Sitka is a larger town than Skagway, but more excursions are offered in Skagway.
Since you are doing a 7 day cruise there is not enough time for Skagway looking at the itinerary. To bad you are not going to both towns, each offers a lot.
In Sitka you can do some of the items on your own as Michaels Cathedral, Rapture Center. The Russian tour is interesting.
You can purchase an all day bus pass in Sitka that will take you to predetermined stops. Saves on a lot of walking. They are small busses and if you get a driver that is talkative will give you some insight on what to do.
Sitka is a tendered port, no real problems but thought you should know.
Skagway highlight to many is the White Pass Railway, fun and great views.
Celebrity Summit in July 2006 goes to both cities, the draw back is that it is a one way cruise. Vancouver to Seward or reverse. Airfare might be a consideration.
We booked the Alaska cruise in Sept 2006, it is a 14 day leaving Vancouver to Alaska then down the west coast to Los Angeles. Have done this before in May and September on prior cruises.
Sea of Cortez on Ryndam 9-28-2005
Round trip Los Angeles to Hawaii, Summit March 26, 2006
Vancouver – Alaska – Los Angeles, Sept 16, 2006 on Summit