TL;DR: A fantastic slim watch that makes for a good daily wear, with startling battery life, and great features for training. Wrist HR tracking is dodgy, and Suunto's proprietary training "measurements" aren't that useful, but as a GPS watch for athletes who want something smaller than a clunky ambit, this is the watch.
Background: I run and backcountry ski 7-10 hrs per week and as a numbers nerd I like to record my activity. I've been using a Suunto Ambit3 Peak until now because it's reliable, fully-featured, and has a long battery life, but I never appreciated how huge that watch is.
The Suunto 5 is a sleeker and slimmer version of the Ambit. It's smaller than the spartan trainers, but still has a little satelite bump on it like the ambit. It's low profile, and looks good enough to be work as a daily watch without screaming I LIKE MOUNTAINS. The buttons are a pleasure compared the Ambit-- easy to use without much force. Settings allow you to change to watch face and color to fit your preferences-- I settled on the digital face with a good-looking daylight tracking ring around the outside, but classic watch hands, or multi-data displays are also available.
Startlingly good. Suspicious of published numbers, I set the watch on constant HR measurement and turned off battery saving functions to see how long it could run in it's fully featured activity tracker modes. The battery went without a charge for a bit over four days of wearing with three activities recorded for a total of more than 5 hours of active time recorded in the high-quality mode. Charging using a typical Suunto clip-on charger that seems compatible with ambit chargers (didn't test). One really nice function is the ability to change tracking quality when starting an activity. When you start a new activity, the watch tells you how long you'll be able to record in each mode based on the amount of remaining battery. Somehow, this slim little thing can record a 24 hour run with high quality when fully charged.
Sport tracking- high quality GPS tracks and customizable sport modes make for seamless use when training and tracking activities. The navigation functions aren't as fully-featured as bigger watches, but for the average athlete this won't matter.
Activity Tracking- wrist HR can run intermittently 24/7 to track baseline HR throughout the day as well as sleep quality. On-watch graphs estimate recovery status and show activity history for the past week. Sleep quality reports matched how I felt, but 'recovery' numbers were dimensionless and hard to understand.
Wrist HR- provided that the comfortably stretchy band is used snugly, the HR tracking works for gentle activity, but I had trouble getting accurate readings when running and skiing. The watch regularly overestimated my HR by 50%, making it somewhat useless for tracking training load with HR. Still, it seems to work well when worn around town and home, making it useful for following recovery and resting HR.
App- Unfortunately, Suunto is still struggling to make a good mobile app. Currently, you can only pair one watch with the app, so I had to unpair my Ambit to sync the Suunto5. Pairing was simple, and upload is fairly quick.The app will push your data out to Strava or Training peaks if wanted.
Bottom line: I like this watch a lot and it will replace my Ambit3 as my daily training watch. I wish that suunto would ditch its arbitrary training/recovery numbers and adopt the TrainingPeak CTL system, which is widely used by athletes. Wrist HR is cool but has a long way to go-- it's good for daily HR and activity tracking but doesn't replace a real strap for HR based training. Still, the watch is sleek, comfortable, and has a great battery, and it delivers many of the functions of Suunto's top-of-the-line watches at just over half the price.