Under maemo, the axis are not the same as on other devices due to the landscape default. However, as the axis orientation remains the same even when rotated to portrait, different axises need to be used under Symbian and Maemo to have the same effect, i.e.
QAccelerometerReading *reading = sensor->reading();
accelXCumul += reading->value(1).value<qreal>();
accelXCumul += reading->value(0).value<qreal>();