My view is a little more pessimistic. Say you average 90 watts output in a moderate pace ride. 6 watts extra is an increase in effort of about 7% to maintain the same speed. To a small motor like a human, 6 watts lost is not insignificant. If you have to pedal 7% harder than a friend you are riding with you likely will tire out faster if you are of similar ability. Also if it is equivalent to 10 feet of climb per mile (I think 10 is more realistic than 6 for most dynos) then on a century ride you climb an extra 1000 foot hill which is something in my book.