From the top I have to say overall we enjoyed our first cruise - 5 days, western Caribbean from Miami; calling at Falmouth, Jamaica and Georgetown, Grand Cayman. Our Concierge class cabin on the aft of the ship was generous in size and very comfortable; comparable to a small room in a luxury hotel. The veranda looking to the rear was extremely large. We were on deck 9, directly below the outdoor dining area and there was some noise from moving chairs, the band, etc., but not a big problem. The steward serving our cabin was very helpful, recognized us on sight the second time he saw us and responded rapidly to requests (such as for morning coffee). We found the level of comfort and service to be worth the additional cost.
We ate most of our meals in the casual restaurant. Next time, we'd do our evening meals mostly in the more formal restaurant where reservations are advised. The food in the casual restaurant was quite acceptable, comparable to what you'd in a good buffet restaurant (think 2 steps above Old Country Buffet). In the main restaurant, the food was better and the service certainly more attentive as you'd expect. We ate one dinner in the "gourmet" (surcharged) Olympic restaurant and found it worth the price. A delicious meal, served in a leisurely old-world fashion.
Breakfast on first morning out exposed a problem in Celebrity's planning - they were slammed in both restaurants because they were not prepared for the 800 or so guests in an affinity group to hit the restaurants all at once (they apparently overestimated the percent that would use room service). This meant unacceptably long waits, cold food, grouchy everybody.
We didn't do any of the evening entertainment options in the lounges or casino (OK we spent an hour on the penny slots); just personal preferences. A Broadway music review we did attend was about the quality of a decent college production. We did enjoy spending time by the pool during the days at sea - people watching, enjoying food from the grill, and a few beverages.
The vessel itself is quite comfortable. There are any number of spaces where one could go and read, play cards or spend other kind of quiet time. The internet service is handy but expensive (75 cents/minute). You can make and receive calls on your mobile phone aboard ship, but check with your carrier to determine what your roaming rates will be. The ship also has a satellite phone service you can use from your cabin, which is probably more costly that your cell phone would be, and there is a toll free number family members can use to get in touch with you.
Unless you're a very heavy drinker you can skip the beverage packages. For our cruise it would have been about $60/day/person. Since the cruise line promotes them heavily both before and during the first day or two of the cruise, you can bet they make our like bandits on this. Since most drinks are around $6-$8 -- well, you can do the math. Similarly, we avoided the many photo ops, souvenir options, etc.
When we take another cruise we'll consider more carefully the ports of call, looking for places of greater historical or cultural interest, where a day ashore offers relatively easy access to its benefits. Interestingly, we did not hear any of our cruise companions talking enthusiastically about their excursions.