My wife and I enjoyed a great cruise from Vancouver to Seward. While it wasn't perfect (if you're expecting a perfect vacation, I wouldn't recommend cruising or ever leaving your home), the food was good, the staff superb, and the ship, while obviously not a newer vessel, was in absolutely fine condition. We are in our 30s -- a younger clientele than many (but not all) of the other passengers.
Food: Olympic was great; perfectly cooked lobster for our splurge dinner, along with impeccable service. The main dining room ranged from okay to very good, with most meals falling closer to the "very good" category. I can't imagine how hard it is to cook for 1000 people every night, so I commend them for getting as much of it right as they did. The buffet was decent but got repetitious. The burgers and fries on the sun deck were great for an easy "fast food" experience.
Staff: We were treated with nothing but respect and kindness. Our waiter and room attendant were both fantastic. The bar tenders were friendly and seemed to enjoy their work and interacting with the customers.
Entertainment: We stayed away from the shows put on by the cruise staff -- they just didn't appeal to us as much as they might have to the older crowd. We did really enjoy the comedians and the aerialists who performed a couple evenings.
Ship: While the Millennium isn't the newest ship, don't believe the horror stories people might want to sell you. It's in fine shape. Our room was clean and comfortable; the public areas were kept in good condition; and I saw nothing that seemed out of the ordinary for a ship of this age.
Excursions: We booked all of our excursions in Alaska through private companies and not through the ship, but greatly enjoyed them. Too much beauty and nature in Alaska to not have a great time off the ship.
Spa/Gym: My wife had a great massage and we both really enjoyed the acupuncture (we'd never done it before). Fitness center has everything you'd need for a week at sea. Too bad we didn't use it more.
The Hiccups: Embarkation took a while - perhaps it could have been better organized. Perhaps not. We also had several problems with our room keys not functioning - required several trips to guest relations and too much time waiting in line. Staff were friendly but should have handled the problem more quickly. Classes at the fitness center were expensive for what you get (we tried yoga), but these were probably also geared more toward the older crowd.
Casino/Bingo: I'll have my revenge!
One bit of advice: We upgraded to the premium drink package and didn't regret it for a second. While neither of us is heavy drinker, when we do drink we like to have a nicer glass of wine, scotch, or a martini with top shelf liquor. With the exception of a couple more expensive wines (and bottles) on the list, we were able to enjoy almost everything the bars were offering. Worth it, in my opinion.