We cruised Alaska in early May and totally agree with the previous posters, a balcony if you can afford it is the way to go. Since the weather was cool we brought up blankets from the pool area.
I also agree with Dave's excursion advice. The White Pass Railroad was great. Our excursion took the bus into the Yukon and returned on the train. Our bus passed a bear and we saw mountain goats on the mountain top. Our stop at Emerald Lake was beautiful. The scenery from the train was also great. We were able to get a seat at the back of our train car, so we could go in and out on the platform easily.