I upgrade to the Edge 305HR after own the 205 for about 5 month and after decide that I want heart rate information to accompany the wealth of information that be already be capture by the 205 . I have use the new Edge 305HR for about 60 mile of combined road and mountain biking . like the 205 it capture a wide range of information about you ride - distance , elevation , calorie burn , etc. . after follow the direction -lrb- which involve wet the sensor prior to put on the heart rate monitor -rrb- , I have find that the heart rate information be incredibly reliable . it be great to see , for example , that on a recent 32 mile ride in a hilly area of Northwest San Antonio that over a hour of the ride be at my target heart rate -lrb- 80 % of my maximum heart rate -rrb- . I upload my info from the Edge and take advantage of the free Motionbased.com account in order to chart my progress . I have experience ZERO problem with erratic heart rate reading , etc. that have be indicate in previous review of this unit . I would suggest owner of the 305HR that be have these problem should review the instruction carefully -lrb- make sure that the sensor be wet and the unit be snug on the body ... just below the breastbone -rrb- or contact Garmin to order a replacement . this unit be work exactly as advertised and will provide a great deal of quality information to help you achieve you training goal .