The Allure is huge, so even being at almost full capacity (6,100 passengers), it didn't seem too crowded. There were lots of kids on spring break, and I'm not sure we would choose that week to cruise again.
The most impressive thing about the ship, besides it's size, is the ability of the ship and crew to manage the population efficiently. With very few exceptions, there were no crowds or lines. It was easy to find places to sit in public spaces. Embarkation was smooth.
Some random notes:
You have to get reservations to the entertainment shows and most fill up before the cruise starts. We were fortunate to reserve ours, but would have preferred to make the decisions on the day of the performance instead. The nightly comedy is adult-only, which is a disappointment if you are traveling as a family. The one night they did family comedy, it was clear the comedians were not meant for this type of crowd.
With the exception of our room steward, we found the crew to be excellent, friendly and helpful.
One downside was that there were very few public indoor spaces with windows.
At dinner, we had a family with 5 kids sitting next to us and the kids would play their electronics and videos when they weren't physically fighting with or yelling at each other. So dinner took on a Chuck-E-Cheese type of ambiance. I think the use of electronics without earphones should be banned in the dining rooms.
The food was average. Some really good things, but mostly just standard fare. The Windjammer was not great, food was often cold and there was no pasta or omelet bar. Giovanni's Table, the specialty Italian restaurant was really good though. We bought the cupcakes from the cupcake store - they were good, but probably not worth the money. Our dining room waiter and assistant were fantastic.
The zip line was not as long as expected, but it was fun. The line moved very quickly so it was easy to get on. The fitness center was great, and the jogging/walking track was fabulous, on deck 5 so there was lots of shade.