Harborside has all the advantages of a timeshare villa with all the amenities of Atlantis. We were very happy with our stay there. Before arrival, I was concerned about the distance between Harborside and Atlantis but not only was it walkable, but the shuttle advertised as running every 20 minutes actually ran more like every five to 10 minutes because Atlantis and Harborside EACH run their own shuttles between the two and you can use either one. We never had more than a few minutes wait. Harborside is also right across from the ferry to Nassau and within easy walking distance to several non-Atlantis shopping/restaurant areas.
Our villa was the smaller one-bedroom floor plan and was a bit cramped for a family of four but not terrible. Our six-year-old slept on the foldout queen-size sofabed and we rented a crib ($10 for the week) for our two-year-old. Actually, the crib was one of the nicest surprises in the villa- it wasn't a travelcrib, but a real metal one with Pottery Barn linens and our daughter who HATES portacribs happily slept in it (I expected she'd be bunking with me all week so the crib was a godsend). We had a kitchenette area with a table for four, a highchair (I requested this ahead, but there was no charge), a microwave (great for morning cocoa and reheating leftovers), a stove for making the mac and cheese we brought from home plus morning egg sandwiches (we walked over to the grocery store in one shopping center off the main road), a dishwasher, a washer and dryer (for wet bathing suits and blankies that were dragged all over the resort each day), and a CD player/VCR combo for daily Barney fixes. The villa was neat and well stocked (dishwasher soap was provided, laundry powder was not). As Starwood timeshare owners, a complimentary mid-week cleaning was provided, but if you're not owners, I think daily maid service can be arranged for a fee.
Harborside has it's own pool with a children's area plus a poolside restaurant. Once a week they have a Bacardi-sponsored pool party with rum punch, Bahamian appetizers and silly games and dancing. Best of all though, Harborside guests have use of all the Atlantis water facilities and slides. Since Atlantis is open daily to many tour groups and visitors, it's nice that their pools and beach chairs are reserved only for resort and Harborside guests, identified by daily color coded plastic bracelets and resort "cards". Service was friendly, but there seemed to be some lack of communication with the main atlantis facilities. Still the Harborside concierge did her best to resolve issues (we had several items disappear into the Atlantis lost and found, but they were small things like a pool toys). We will definitely be returning here and highly recommend Harborside. I think you get much nicer rooms, more space, and much more amenities than at all but the nicest Atlantis rooms.