This was our first cruise with Celebrity so my comments are from the experience on this ship and by comparison with HAL, RCL etc.
Boarding, Sydney International cruise terminal is a great location however it is sadly lacking in quality and efficiency which is a shame.
Cabin, we booked and Aqua Class cabin, 9085 which is under the pool deck but the noise was minimal. The cabin was very good in all aspects, shower fantastic, real towels and as always cabin staff excellent. One issue I personally found annoying was the lack of information on the TV regarding the ships location, where we have been, going to, speed etc etc.
Dining, being Aqua class we dined in Blu which is exclusive for Aqua class and it was a fist class dining experience. The menues were high quality and diverse, service fantastic, layout great so overall excellent. As this restaurant was so good we looked at all the other venues but did not dine there as Blu had a superior offering, all round.
Entertainment, new shows every night which was very good, a few other entertainers around the bars who were good. There were excellent speakers on board who's presentations were all related to the USA and world history events. They were very interesting however we were sailing through the great barrier reef and Indonesia so I thought topics more relative to our locations would have been more appropiate.
Ship, the ship is hgig quality having just been refurbished, easy to get around and all the facilities you could ask for. Being large has its drawbacks as we had to tender at many ports and that was very time consuming and frustrating.
Overall a great cruise and the Celebrity experience was for us, excellent.