We had already sailed with Celebrity Constellation and we already knew what to expect, so this time we opted for a cheaper inside cabin (yes, choosing the right location in the ship, deck 8 to the fore).
The interior cabin was pretty good, individually controlled air conditioning worked perfectly and we did not have any odor problems.
Cabin is the same size as the regular balcony cabins but without any exit, all the back wall is a large mirror which makes space look bigger.