I owned a Garmin 920XT then a Fitbit Ionic (died after 2 years) before the Suunto 5. I bought the watch based on reviewers praising its accuracy (which has proven true). Running routes with known mileage markers, looking at reported tracks on the Suunto app and comparing routes from group runs on Strava, I have been very happy with the accuracy of this watch. Kudos to Suunto! Also, I am super happy with all the different metric reporting options during exercise tracking. Amazing! So much better than Fitbit.
I was looking to replace my Ambit 3 that was lost. I primarily use it for running, indoor workouts, and climbing. As compared to the ambit, the Suunto 5 has a smaller profile and is much more comfortable. I like amount of data I am able to display while running and being able to customize that data. I have not found much utility in the activity or sleep tracking. The wrist base HR seems to be hit and miss for me, but it seems to work better once my wrist gets a little sweaty and when I have the strap tighter. The strap is a bit more elastic than the ambit which allows me to wear it a bit tighter but still be comfortable.