Bests & Worsts Reviews from Amazon

Got mine last week from REI -> Coming from the F2 then F3 this is a worthy upgrade. It essentially is the F3 sapphire with a optical HR sensor recording 24x7 HR data, including resting HR data. I enjoy the new strap as well - slightly softer and a touch more give then the rubber F3 strap. The bezel also does away with the red accents replacing them with silver. Also the sapphire glass is flat not domed. You will have many say oHR sensors are still "inaccurate" and that is mostly true but it all depends on the user, potential usage and expectations. I find the elevate oHR sensor to be excellent for most training runs, and for daily HR tracking. Once you begin to get into sprint intervals, hills and other types of extreme HR fluctuations is where you begin to see the limitations of the optical technology. However most serious runners will be using a chest strap paired with this watch, which I also do. So far three workouts in with the F3HR - 1. 3 mile run wih F3HR on left wrist and I also wore my ambit 3 on right wrist with sunnto chest strap hrm. results: after an indoor warmup I headed out - both units tracked within 1-3bpm from each other from the start. Pretty happy with that. 2. Cross training indoors – Same setup with both watches – burpees, medballs, pullups, pushups, sled pushes and etc… The only noticeable difference was a few second lag for the F3HR to catch up to the suunto. Both average HR were only 2bpm off at the end of the 45-minute session. 3. 15 mile trail long run pace – F3 (non-HR) with garnin hrm-run + F3HR on opposite wrist - during the first mile the F3HR was about 10-15bpm below the HRM-Run - after things settled in they both tracked nearly identical for the remainder of the run except for hills. I should note I walked the uphill sections and the F3HR did show about a 10-15 second lag when the HRM-Run was spot on. So if you need this immediate data for some reason the HRM-Run is still tops - but at the end of the run the average HR were both nearly identical. 4. Ran my first race with the watch - a muddy, gritty 50k - I opted for the HRM-RUN chest strap so for HR data not much to reports. GPS accuracy (GLONASS ON) was spot on - Watch behaved super responsive compared to my older F2, as a matter of fact comparing the two gps track recordings from a friend who ran (used his F2) the F3HR has a better track - the F2 was smoothed much more than the F3HR. Review in progress...