Reviving this thread from a year of inactivity. My husband and I just returned from our second stay here, 4 nights over the Labor Day long weekend as part of a friends group trip to Oahu. The hotel had a 4th-night-free promotion which was reflected on the average daily room rate on OTAs, and I managed to double dip with the Citi Prestige 4th-night-free, resulting in a fairly deep discount for the stay. We booked an ocean-view room and did not get (and weren't expecting) any upgrades, but did get early check-in when we arrived around noon.
For comparison, our previous stay was in January 2017, and -- maybe because it was still recently opened -- we found a really sweet rate at ~$300/night for the mountain-view (lowest tier) room. They upgraded us to a really nice, spacious ocean-view room (with a small amount of parking lot visible from certain angles) with a sofa and lanai. This time around, the ocean-view room was smaller (no couch but a bench at the foot of the bed) and had more parking lot visible that the lanai was mostly solid concrete(?, as opposed to all railing) to block the sight of the parking lot. So from the room and cost perspective, we definitely got the better deal 2 years ago, but wouldn't have it been 100% satisfied if I didn't have a previous stay for comparison. The valet parking also went up in price.
There were a pretty good list of daily activities which we didn't remember them having in 2017 (maybe why the rates were so low back then?). There was a special hula performance the evening we arrived on the lawn at sunset. We both got facials at the spa and enjoyed the treatment and the facilities. Pricey, but what we expected for a luxury resort in Hawaii. We did really eat on the property except for lunch or cocktails at the pool and breakfast the day we left. In 2017, we tried Noe, the Italian restaurant, and found that Monkeypod, Roy's and other restaurants within walking distance were a better value.
When not exploring Oahu, we spent most of our time at the lagoon beach or adult pool. Our favorite aspect of the 4S Ko Olina is the adult pool; we like it more than the ones at the 4S Maui or Hualalai. Because of its length, it never feels too crowded swimming/floating in there. As for the beach: yes, it's a man-made lagoon and not as beautiful as, say, Wailea on Maui, but the water is calm and safe. We especially appreciated that after we both got stung by jellyfish at Kailua Beach Park. A dozen friends were also in the Kapolei area at the same time, but the others stayed at an Airbnb in Ko Olina or the Hampton Inn in Kapolei. One day, one couple with a toddler joined us at the Lagoon and shared our 2 beach chairs (the staff were nice enough to bring us 4 waters, even our friends weren't 4S guests). The kid had a blast as the lagoon beach was perfect because he was still afraid getting into any body of water with waves. He initially sat back from the shoreline but high tide eventually rolled in and he got used to playing in the water without even knowing it. The other DINK couple on the trip also walking around the hotel with my husband, and immediately regretted being unnecessarily cheap by staying the entire week a 15 min. drive away at the Hampton Inn and trying to find parking at the lagoons.
Overall, we would still consider this our go-to hotel for Oahu for all our needs, despite getting a slightly worse room than our first stay. Obviously, if you're looking for more action, Waikiki would be the way to go. Or split a 1-week visit before this area and Waikiki.