Hi,
We just got back from Harborside this weekend. It was really really nice - lots of things about it that I liked better than
DVC rooms - and you do have full use of atlantis facilities. With DVC points you stay at one of the three different hotel towers at Atlantis - Beach Tower, Coral Towers or Royal Towers. The beach towers front entrance and exterior are pretty run down - don't know what the rooms look like - coral towers are nice and centrally located between all the pools. I think Coral Towers would be a good compromise if you didn't want to spend the extra points on Royal Towers. All the common areas - pools, gardens - are nice.
I believe a few years ago you could do an interval trade to harborside - I don't think you could ever use points on a nightly basis. We got a trade into Harborside using a sheraton week we own. Like I said - we really had a great week - but food is outrageously expensive (so a kitchen is a great asset). Like an ice cream bar at the pool fast food place was $7. and everything has 15% gratuity added. A bottle of water is $7...you get the idea. So a week of food there costs about the same as a week of food AND park tickets at disney. Even the kids clubs were so much more (a 4 hour evening with pizza dinner was $60 per child) I'll never complain about disney food prices again! What I did find is that the "expensive" restaurants were a better value than the cheaper places. Like a Johnny Rockets just opened in Marina Village on the property and it took an hour to get: 2 chocolate milkshakes, a chicken sandwich, a turkey burger, a plate of fries, 2 kids meals - and the total cost of that: $70! Then we went to Dune and had wine and appetizers and dessert and lobster, etc in a beautiful restaurant on the beach - and it was $150 - expensive - but well over twice as good as Johnny Rockets! And without a car you are a bit stuck since a cab downtown for a family of 4 is $20 - and it's only about a 5 minute drive but they charge per person. So you could find some cheaper places downtown but you have to add a $40 cab fare to your dinner which probably negates any savings...
I would go back again - the kids had a great time in all the pools and the people there are extremely nice and the ocean is beautiful. But I think I'd like to go to a different island that isn't so built up - maybe Exuma.
Good luck!