I buy the watch primarily to help I maintain a pace while I train for a half marathon . the only function I really use on it be the time , distance and speed . I do wear the heart rate monitor but do not concern myself with it too much . anyway , I have validate the distance and believe it to be accurate . I trust that the time be accurate as well so it would stand to reason that the speed be , also . I download my datum to the pc and it be neat to look at , pretty cool to view it in google earth , especially my hike . I know there be a lot more functionality to the watch that I be not exploit but it be serve the purpose I buy it for . I 'll say the watch be a bit bulky but I do not notice it be heavy at all . I would recommend this watch .