I followed up my comparison of the Band vs RunKeeper on the iPhone by switching the wrist I wore the Band on. Moved it from left to right wrist.  As I am right-handed and my right wrist has greater circumference than the left, the Band seems to fit a bit tighter but was always fairly tight on left, too.   So .... for essentially the same run I  got hugely different calorie counts from the Band.  The results with Band on right wrist were about 60% of those on the left wrist. And heart rate was similarly lower on right-side.  Whatever Microsoft is doing to try to measure the heart rate -- which this thread says is then used to estimate calories burned -- seems to be very undependable and misleading.  So much so that their advertised promise of " Microsoft Band ... helps you achieve your wellness goals by tracking your heart rate, steps, calorie burn, and sleep quality." is really not true nor honest, IMHO.  I am pretty disappointed.  I did not expect 100% perfection but this level of performance is beyond being what Microsoft should find acceptable.