We booked a 3 night stay on Aitutaki after our one week stay on Rarotonga. Although we stayed at a fantastic resort on Raro, I have to say that we were not disappointed in Pacific Resort. From the minute we arrived and were greeted at the airport in a small private lounge, to the personal greeting at the resort by its manager, Michael, we new we were in the lap of luxury.
Our spacious villa was right on the beach with a beautiful view and awesome sunsets each night, enjoyed on our deck with a glass of wine. Aitutaki is more laid back than Rarotonga, if that is possible, and I highly recommend you hire a scooter to bomb around this small jewel of an island. There are not a lot of restaurant choices outside of the few resorts here, so we found ourselves eating at this resort all three nights. The food was excellent right from the menu offerings to the presentation and flavor. The staff was very friendly and helpful. We did some snorkeling right in front of our villa and saw lots of colourful marine fish and juveniles. Snorkeling gear is available to borrow but I would recommend you bring your own mask and fins for personal fit. We did some diving while on Aitutaki with Bubbles Below and I would highly recommend this outfit. We met another diver on one excursion and she dove with the "other" dive outfit and definitely preferred Bubbles Below's operation. All gear is provided in the dive cost which seems common on both Aitutaki and Rarotonga.
As this is the tropics, you should bring some insect repellant for the evenings, mostly at dusk. You will also encounter small ants on your deck but that's expected as you are on the beach. Mosquito coils are provided in each room and we put one out on the deck for the evenings where we watched the sunset. The mossies were less bothersome there than they are at home :-)
There is not a lot to do on the island so 3 or 4 nights might suffice unless you truly want a romantic quiet vacation. From what I heard from friends staying at another resort and from what we saw, Pacific Resort is the jewel on Aitutaki.