You might want to cruise over to the "Cruise Lines" area and post under the NCL topic.
We have friends who were on the Inagural of the Sky and loved the ship. There have been some slightly negative reviews, too.
Nassau can be a little nippy in the winter months. It mostly depends on the day or the week. I wouldn't go without a cotton sweater, just in case.
You will be able to adjust the temperature in your stateroom to whatever you feel comfortable with. The dining rooms and show lounges can be a bit chilly, so take along a shawl or something to cover your arms if you tend to feel cold.
Keep asking! Plenty of folks will be along to help out however they can.