We've sailed on all the Celebrity Millennium-class ships, and can't say enough good words for them. My wife loves the warm salt-water Thalassotherapy pool, and we both find the dining and entertainment options more than adequate for our needs.
We aren't big onboard spenders - tips and duty free liquor are the bulk of our end-of-cruise bill - yet we don't feel at all deprived. Though tempted to try Qzine, we passed, as the MDR service and food was great.
We've made it to Elite status with Celebrity, and cannot pass up the continental breakfast with complimentary coffees and cocktails, or the evening happy hour and other events.
Sometimes it pays to ignore the advice given by the cruise line: The ship was scheduled to depart at 8:30 pm, and our e-docs suggested that we not queue for boarding until at least 2 pm. We arrived at the pier at about 12:30, found short, fast-moving lines and were aboard before we knew it. Rooms were available shortly after we'd had a couple glasses each of complimentary sparkling wine, so we were unpacked and settled before the 'recommended' check-in time.
Our trip was a repositioning between the winter home port in San Juan, PR and Cape Liberty, NJ. Of stops in the USVI, BVI, St. Maarten and King's Wharf, Bahamas, we enjoyed the Bahamas most. The other ports - and especially Tortola, BVI just seemed to be shopping centers for the same t-shirts, watches, diamonds and other tourist magnets as you find everywhere.
One interesting sidebar: While in the Bahamas, two 50-ish women passengers and a Jamaican cabin steward were arrested for trying to carry 3 kg cocaine into the country. Celebrity kept it quiet: We heard nothing about it at the time from either the cruise line or other passengers.
We will happily sail on the Summit again - but first we have trips planned on the Infinity and Silhouette!