Just returned from the September 1 sailing to Canada. What a treat! I've sailed with Crystal on two occasions, and the Serenade of the Seas was a far superior cruise.
The ship is absolutely beautiful and the staterooms are intelligently designed and quite comfortable. Service is excellent. Chops Grille lives up to its reputation of having the best steaks and chops on the high seas. The coffee at the Windjammer is great! The atmosphere is congenial and relaxed.
Unlike Crystal, where you are bombarded with high-pressure sales techniques to encourage you to buy, buy, buy, extras on the Serenade (such as specialty restaurants, tour excursions) are for you to enjoy or not, depending on your inclination.