I have used it twice since it's been updated to leverage the HR monitor. Yesterday, I ran 7+ miles...the app had the issue of not stopping, just like other people have experienced. I stopped the run from my iPhone and lost my HR data. After the run, I noticed that the app was updated in the app store again so I loaded it hoping it would resolve the issue. And it did for the most part. I just finished a 5 mile run and I was able to stop the run via the Apple Watch...it was definitely fiddly. I long pressed it, hit the stop button and it went back to the time/distance/pace screen. I long pressed it again and hit the pause button bc the run was still active. And sometime during that, the activity stopped and uploaded HR information to the app. I'm thinking when I hit the stop button, it starts uploading the HR data and it takes some time to finish uploading. Anyway, it's a little annoying but I'm happy I'm finally able to use the HR monitor function of the watch.