Harbourside is a beautiful part of the Atlantis resort, and it is a lovely walk each day to the Aquaventure part of the property, which is the highlight for kids.
A few nits to pick, though.
A 4 PM check-in is late in the day, when coming from colder climates. We weren't really offered a place to change into warmer climate clothing, so we were hot and sweaty, and wanting to get to our room... which wasn't ready until 5:30 PM. Not so good...
...and then when we did get into the room (which was actually STILL being cleaned when we arrived), they neglected to clean one of the bedrooms - which had hair in the shower and a lipstick-covered towel hanging in the shower area. Absolutely disgusting. Atlantis, you can do better than that.
We asked for more towels on the first day, and blankets, as the room was cold at night, and our request was ignored. We asked again on the second night, and we were rudely told "These are the last towels you will get during this stay." Why not tell us that we are expected to wash and re-use our own towels? (The units have washers/dryers.) There is no housekeeping at all - they do not come to make beds/change sheets/empty trash.
Harbourside is near the Marina Village, which you can usually walk through to get to the hotel, except it is now fenced off, blocking access. Stupid.
Lastly, 1/2 of Atlantis is 1/2 open, so you are paying full price for 1/4th of the resort. We still loved it and had fun and great weather, but beware...