The funeral orations give insight into Gregory's oratory skills as he lauds fellows saints after their passing. Interestingly, he seems to hint that his father was part of the Christian fold, even at a time in life when he followed another religious sect, on account of his morality.
The theological orations are great reading for insight into the moral requirements of doing theology and working through the arguments for the divinity of the son. I think his oration on the Spirit is one of - if not the - first time that 'Theos' was used for the Spirit.