Absolutely superb stay in Conrad Koh Samui.
The villas are no doubt amazing, every villa enjoys privacy with their own private pool and views to the ocean or the Five Islands, and the villa size is huge as well. We stayed in the Oceanfront villa Room 208, but we had a nice view of the Five Island. Pool in the villa is saltwater. The bathroom is almost the size of the bedroom! There's a (very) huge bathtub in the bathroom, and a separate shower area, and separate toilet with bidet.
Going from the villa to the restaurant, spa, lobby, beach would require a buggy as the roads are very steep and it's quite a long walk. Luckily since Room 208 is nearby the restaurant for breakfast as well as access to pool & beach, we can walk and don't need to wait for buggy. When we were there we always get a buggy quite quickly too, no long waiting time.
Location is secluded, so it's perfect for a lazy, resort vacation. The drawback is of course it's a bit far from the "city center" and the airport (~45 minutes drive) and convenience store/other restaurants, but this was no problem for us because we just wanted to maximize our time in the resort.
Service is impeccable. I'd like to especially mention Goy who served us at Jahn, who made the dining experience much more enjoyable, as well as Jack Huang who helped us during our stay.
There are free activities provided including yoga, kickboxing, etc but we didn't get to do it. We went for kayaking which was also free. Other free activities include paddleboarding and snorkeling. Note that the beach & sea is quite rocky so not a lot of corals to snorkel. We went for excursion arranged by the hotel (at an additional rate) to Pig Island & Koh Tan.
All in all very enjoyable experience in Conrad, which was a perfect secluded, lazy beach vacation for us.