So over the last 3 days, I've run 15 miles using the Workout app on the watch. These are routes I run regularly with my Garmin watch, Strava on the iPhone. They all produce 5 miles consitently. The watch, however: Run #1 (Road): Garmin 5.19 miles, Apple Watch 5.01 miles Run #2 (Road): Garmin 5.18 miles, Apple Watch 5.01 miles Run #3 (Trail): Garmin 5.2 miles, Apple Watch 4.62 miles I've had my iPhone 6 with me for all 3 runs (so the watch should be using the GPS) with no other running apps in use on the phone. I've read some people's Apple watches are spot on, some are off like mine. Just like to get ideas/feedback from all my fellow watch runners out there!