My wife and I took a cruise on Crystal Serenity Nov. 30 – Dec. 11, 2014, from the west coast of Costa Rica, through the Panama Canal, up the east coast of Central America and Mexico, ending in Miami, FL, USA. We're not members (yet) of the cruiser subculture. Our only prior cruise was on the Crystal Harmony in 1996, so we have nothing with which to compare Crystal.
That having been said, our overall experience was excellent. Crystal is on the pricey side, but you get pretty much what you pay for. Crystal's marketing hype is over the top, so we came in with very high expectations. Mostly our expectations were met, one was more than met, and a couple not quite. Still, for the price we think it's a good value and would consider taking a cruise on Crystal again if the time and place were right.
The passenger crowd is mature. I'm in my early 70s and may have been slightly on the younger side of the average age of all passengers. There were no children that we saw on the cruise, and the ship is not geared at all toward children.
The room is small, which is made clear in the promotional materials, but very nicely laid out and well appointed. (There was, however, a strange art print on the wall across from the foot of our bed -- some sort of amateurish fantasy castle and village scene.) The room was just fine for us. On one day the ship opened up some larger cabins that weren't take so the passengers could have a look. The 8000 (where ours was) and 9000 cabins are all 269 square feet, including veranda. The penthouse with veranda model on 10000 deck, though at 403 square feet including veranda felt little larger. On the 11000 deck there are some 538 foot suites, two rooms divided by a curtain, which give you more of a small hotel room feel, at a cost. We talked to one couple that had taken two of the 269 square foot cabins, which wouldn't be a bad idea if you are willing to pay the price.