Summit is mid-sized, and virtually everyone we spoke with said it's that perfect "not too big, not too small" size. For sure, it is pretty darned impressive, but this was our first cruise ever so we are making no comparison here. One very experienced Celebrity cruiser we met said that while it certainly is beautiful from its recent renovations, when you look closely you can see some signs of aging that you just don't see on the newer ships. I will say that each of the venues, whether restaurant, lounge or outdoor area was just great-comfortable, clean and new. Here is where I could write a book but I will restrain myself and comment on two: the hip, lively atmosphere and very entertaining servers at the martini bar made it our first stop every evening, and the Thalassotherapy spa was the most entrancing hot tub experience there is (best experienced while actually out at sea, for the effect of the swaying of the boat).
As for the upcharge restaurants, none of them could make the main dining room, The Cosmopolitan pale in quality. And while they do give the feeling of exclusivity, keep in mind that if you go with the Select Dining package you can always have the benefit of reserved, private tables in the main dining room, but still have to pay the upcharge in the other restaurants. That being said, since we saw no sacrifice in quality in the main dining room, we actually never went back to any of the upcharge restaurants a second time. The ship's buffet, Oceanview Cafe did leave us wanting for more choice and better quality. Anyone who has been to Vegas will understand when I say this wouldn't compete with even the least impressive of the big casino buffets.
With a 1-to-2 ratio of crewmember to passenger, you basically have 2,100 passengers who do not have to lift a finger and there was never a shortage of clean table or available lounge chair. Empty drink glasses and dirty dishes and used towels were hardly ever visible.
We took cabin 9160 which is Concierge Class, facing aft. While the cabin itself was standard for Concierge Class, the balcony was a wow for two reasons: spectacular views, especially when leaving port, but also while at sea as the wake left by ship is beautiful to look at and calming to listen to; and the balcony itself was much, much bigger than the balconies on the side of the ship. At about 9' x 12', it had a table and 2 chairs (but which could easily seat 4), 2 additional arm chairs and 2 chaise lounges and ottomans, and still it wasn't cramped. Another recent review of this very cabin mentioned the drawback of hearing the noise from the bar deck above, but it actually worked to our advantage as each evening at sail-away, we enjoyed the calypso music of the sail-away party directly above, from the privacy of our balcony.
In a nutshell, this was our first cruise, and we feel we don't need to try another line to know that Celebrity is a really great line and this was a really great ship.