Really good item...I can't see anyone really building tear much anymore other than the few obvious exceptions. Many mana hungry champs can build this item instead and it'll probably be much more efficient than tear or RoA.
Do not buy this item on a support :< you can spend 3k on some other useful items for support. like aegis and shurelyas for that gold. this is just going to be like one of the best items for casters. making opnivia even more op.