I've been using my HAC4 for 4-6wks now and it seemed that my power output was low (avg ~100watts) even though my performance was med/high (21-23mph avg on flat @ 240lbs rider+bike+equipment). I went to the analytic cycling page and based on my numbers I should be registering ~300 watts, far from the ~100 the HAC4 is telling me about. So then I opened this poll to see if I was alone http://www.cyclingforums.com/t175831.html turns out there looks to be two groups. One group down around 100ish and the second up around 2-300. Very weird... I blame the HAC4 algorithm's dependency on altitude gain, it seems if your not gaining altitude you can't exceed 100 watts easily even at 21mph @ 240lbs on the flat/slight incline (<2%). Anybody else???