The fourth iteration of the Apple Watch still looks like a tiny iPhone on your wrist, but for many, it was the most exciting device announced at Apple's event earlier this month. A larger screen, faster performance with improved sensors, fall detection, and ECG readings are just a few of the features that inspired quick interest in the Apple Watch Series 4. The steps forward in health monitoring alone point to a new era for Apple's wearable, and users who could benefit most from them have a compelling reason to shell out $399 or more for the Series 4.

Otherwise, the Series 4 is an amalgamation of small improvements that make a big difference in the Apple Watch experience. These improvements will attract new users to the Watch who have been waiting for a device that's up to their personal standards, and they will make existing Watch wearers question their happiness with the smartwatch currently on their wrists. But while the Series 4 represents the first major redesign of the Apple Watch since its birth, that alone doesn't make it an automatic upgrade for all Apple Watch users.

The hardware

Models and pricing

The Apple Watch Series 4 comes in two sizes—40mm and 44mm—and as either a GPS-only device or a GPS-and-cellular device. The 40mm, GPS-only Series 4 Watch with an aluminum case starts at $399, and the GPS-and-cellular Watch of the same size starts at $499. The 44mm, GPS-only model starts at $429, and adding cellular ups the starting price to $529. Stainless steel cases are only available with GPS and cellular capabilities: a 40mm Watch costs $699 while a 44mm Watch costs $749.

All models come standard with either a sport band or a sport loop band. The special edition Nike+ Watches have exclusive Nike sport bands, but the bands don't affect the prices of those models. A few GPS-and-cellular, stainless-steel Watches come with the premium Milanese loop bands, and they cost $799 and $849 for the 40mm and 44mm sizes, respectively.

Those who have bands from old Apple Watches are in luck—all old bands will fit on the new sizes. Prices for additional bands haven't changed: a sport band costs $49, while a Milanese loop (as well as special leather bands) costs $149.

The Series 4 comes in an Hermés collaboration edition just like previous Apple Watches. These luxury devices start at $1,249 for a 44mm stainless steel model with a single leather band.