I've just got back from a great trip to Rarotonga in which I went on the Aroa Pony Trek. (November 2007). The ride started out with a trek down Aroa Road where you could see a little of island life inland down a quiet road. My friend who came with me was a beginner, the horses were cute and definitely knew where they were going which made it incredibly easy for her. We crossed a road and headed to the beach which was beautiful, the horses really picked up at this time and you were able to canter/trot at your own pace. Wigmore's waterfall was small, yet it was beautiful. We all had a quick dip to cool off, then headed off back down to the beach and a swim in the lagoon with the horses. The weather was beautiful, the guide was fun and easy to talk to and made sure that we were all comfortable on our horses whether we were beginners or not.
If I was to head back to rarotonga I would definitely take other people on the horse trek. It was throughly enjoyable and I would reccomend anyone who is comfortable on a horse to spend the time in going on the trek.