Rolling take offs in a Helicopter

[tartare]

Fixed wing pilot question.
I had understood translational lift as being when your forward speed gets to the point that the airflow `sees' the main rotor as a solid disc, and you get lift from the disc in the same way that you'd get lift from a fixed wing (i.e. air flowing over the disc).
I've noticed when taking off as pax in a helicopter that there is a `woosh' feeling above certain forward airspeeds - the machine kind of swoops upwards, and had assumed that was the onset of translational lift.
Yet some of you are talking about obtaining translational lift at quite low forward speeds... how so?
Am I visualizing the whole concept incorrectly?

EDIT: OK, Googled ETL and now have a slightly better idea I think. Vector of main rotor thrust points rearward due to forward motion as well...