I like it as a nickname but for a full name it looks too short. I'd like Arra as a full name (as long as it was pronounced are-a and not like arrow but with an a on the end).
It would be good as a nn for:
Arabella AraceliAradhana Araminta AdaraAldara AmaraAzaharaInaraJahanaraMaiaraManyaraNaiaraSamaraSitaraStelaraTamaraXiomara