Having just returned from our Alaska cruise a few weeks ago, I would definitely agree with Dave--a balcony is worth the extra money. It's awesome to wake up in the morning, open your drapes, and see mountains and glaciers. What a way to start the day!
Another plus is that if you get cold, it's easy to go back into your room, warm up, and go back outside without missing any sites.
If you are ever going to splurge on a cabin, this is the time!