ORIGINAL: Rat1
I ran mine for a bit to run in the motor and it seemed to help out in the power department. Also it seems to have a little more power each time I fly it.
The batteries typically need to be cycled a few times to reach their full potential. If you run them down till the speed control cuts the motor off, let them cool 5 minutes, then charge them fully, after the 3-5 cycle, they will have reached full potential. That is probably what you are experiencing as well as the set-in of the motor brushes.
Good luck with it.