When Apple first introduced its Apple Watch in fall 2014, its rough combination of features was effectively guesswork. The operating system crammed tons of iOS-inspired features into a new form factor, and attempted to approximate the experiences that Apple Watch wearers might expect. Maybe, Apple thought, users would check emails on their Watch. Maybe they’d prefer fitness-oriented features. Or maybe they’d want to peruse their favorite photos on a two-inch display in between meetings.

Ultimately, three generations of Apple Watch software have helped the company confirm or disprove its initial assumptions about what would make a great wearable product. People do, in fact, like fitness features. They don’t, as it turns out, care all that much about stock prices on their wrist. Apple Watch, perhaps unlike any other first-generation Apple product in recent memory, was partly misaligned with users’ actual expectations, but the company has been aggressive in tweaking both hardware and software to better accommodate those real-world use cases.

With Apple Watch Series 2 and watchOS 3 alike, Apple has tweaked its initial assumptions about what makes a great wearable UX based on what users actually used.

For its part, watchOS 3 represents what Apple Watch software always should be, and doubles down on the ways people should and do use wearables. The operating system designed for a wristwatch now emphasizes speed, efficiency, and glanceability in ways it never did before, rearranging core parts of the user experience to feel more fluid and immediate. Everything that has been added, removed, or revisited in watchOS 3 is in service of making the platform quicker to use and more aligned with how users experience wearables.

Everything that has been added, removed, or revisited in watchOS 3 is in service of making the platform quicker to use and more aligned with how users experience wearables.

For third-party developers, Apple has loosened the constrains on what an Apple Watch app can be. Following its addition of native watchOS apps in watchOS 2, Apple has gifted developers with the tools and UX best practices necessary to design Apple Watch apps people will love to use. Third-party watchOS apps have become more powerful, more accessible, and more engaging than ever before—and there’s never been a better time for iOS developers to dive in.

The complete marketer’s strategy guide to watchOS 3 in available below.