The Apple Watch Series 2 adds GPS and waterproofing to the first-gen watch, making the Series 2 a legitimate running watch. The GPS tracking is excellent; the HR tracking is good and equal to other devices. The usability is very good – the screen is sharp and readable in bright sunlight. The battery will last 5h with GPS and HR on. Those needing workout data export will need to wait for third party apps to be updated to support the onboard GPS.