This is written by two sisters in their 20's. Side note..the age group on this cruise is kinda on the older side. There were about 100 cruisers younger than 30!
Sister 1: We took our very first cruise with Princess Cruises to Alaska on 07/27/09. It was AMAZING. We were 1st time cruisers, so we were worried about getting seasick. We even got a prescription patch which we ended up not needing. We were a large group of travelers and only 2 of our group got a little motion sickness one day but that's about it. I personally didn't feel too much "motion in the ocean" except when I was sleeping. And of that, only 2 of the 7 nights was there a significant amount.
As for the weather...I have one word: PERFECT. The cruise director did say this was one of the few cruises where there was 7 days of sunlight. But bring jackets/sweatshirts. It gets a little cold while traveling around Glacier Bay National Park and College Fjord.
Being our 1st cruise and not knowing what to expect, we got a balcony and inside room. The balcony was WAAAAAY more worth it compared to the inside room. There were no windows and it was dark and tiny and congested (inside room). Oh, and the bathrooms are TINY.