Pros:
I think the heart rate monitoring is pretty accurate.

I think it accurately counts steps and roughly estimates distance through the day.

I use Strava exclusively for runs. The Strava watch app is good and now it will utilize the HR from the watch.

The outdoor run distance correlates well with Strava distance.

Cons:
The indoor run distance significantly overestimated distance.

It significantly underestimates calories burned compared to different apps. I realize that calorie counting is very subjective.

Sometimes it seems to randomly end my exercise. Perhaps I hit something on the screen while running.

I was really bummed about it before Strava could access the HR. I'm happier now that it is integrated.