DC Rainmaker's Ray Maker spent about three weeks with the Apple Watch Series 12 and came away with a clear line: the new heart rate features only run on the Series 12 and the Ultra 4, and they aren't going back to older watches. His review, published October 2, puts most of its weight on the new Readiness Score.
The score runs from 0 to 10 and comes with one of four labels: Recover for 0 to 1, Pace Yourself for 2 to 4, Ready for 5 to 7 and Go for it for 8 to 10. It draws on fitness, overnight vitals, daytime vitals and your sleep score. The watch needs seven nights of sleep data, at least four hours each, before it shows a number. Garmin's score also moves through the day, while Whoop and Oura give one score each morning. Apple's belongs with the first group.
In Maker's testing it behaved the way you'd hope. He woke up to an 8. After a two-hour road ride the watch dropped it to 5, and after an evening track workout it fell to 3. A week later, when he was sick and had stopped training, it showed a 1, and the watch told him whether low vitals or low sleep was the cause. The score also had gaps: it sometimes showed no value for seconds or longer. A firmware update a couple of days before he published helped, but Maker says the feature clearly wasn't ready when the watch launched.
Apple compares your daytime heart rate variability reading at a given hour with your history for that same hour and leaves out any time you were moving. For an active person, that means very few data points and a baseline that takes well over seven days to fill in. Maker calls it uncharacteristically confusing and messy for Apple, and says daytime HRV isn't very useful anyway.
In the first week the watch barely made 24 hours, even with one to two hours of GPS use. By the third week he was getting the usual day to a day and a half, against Apple's claim of over two days. Charging is the stronger story: five minutes gives about 10 hours of sleep tracking, 30 minutes reaches 80% and an hour reaches 100%.
The Series 12 has no Precision Start, so there's a three-second countdown before it starts searching for satellites. Workout Buddy, Apple's voice coach, still got details wrong in nearly every workout, including kilometer markers. The depth gauge reads to 6 meters and isn't certified for scuba. And Apple publishes no battery figures for the new Extended and Max Extended workout modes on the Series 12.
You need an iPhone 11 or newer running iOS 27 to set the watch up. The Audio Intelligence features need an iPhone that supports Apple Intelligence, which means an iPhone 15 Pro or any iPhone 16, 17 or 18. If you own a Series 11, the Readiness Score is the reason to look, and it's the part Maker found least finished.