dadaumpa:
Regarding pinMode(), that's curious. You mean it has no effect on A6/A7 because of their analog, input-only nature?Because the page http://arduino.cc/en/Tutorial/AnalogInputPins actually uses pinMode() on an analog pin. Ok, that's obviously to set it as OUTPUT. INPUT should be redundant, since they are input by default. But I thought it was a good measure to set them to INPUT, just in case some code previously had set them in OUTPUT mode...
The first six analog pins do have digital circuitry behind them, so pinMode and digitalWrite work just fine. It's just pins A6 and A7 on the surface mount '328 which are analog-only.
Cheers!