In the Triratna community, who I practice with, we see going for refuge to the three jewels as our central practice - the three jewels being the Buddha, Dharma and the Sangha. In fact the name Triratna means the three jewels. However the founder of the movement (Sangharakshita) makes the stronger claim that this is the central act of all Buddhist traditions. The Triratna movement is an explicit attempt to return to that core teaching.
However I'd really be interested in the perspectives of the different Buddhist traditions on that. Does that ring true to people in their own practices. Is going for refuge the central act of Buddhist practice?