Ah. Thank you.
In importance how does he compare to, say, Basil or the Gregories? Or Augustine of Hippo, John of Damascus, or other Orthodox theologians?
As Orthodoxy is branching out and absorbing more of Western culture, I think we will start to find pre-Schism Western saints grow more and more in popularity and influence. St. Hilary of Poitiers is well known and well cited by some Priests, while others will treat him much more obscurely and focus on other, 'local' Saints. That being said, he is a very important Saint. Within certain circles, you will hear parts of his De Trinitate, De Synodis and Commentaries on the Psalms quite often. Universally in Orthodoxy, I would not say he is viewed in the same light as the Roman Catholic or other western Churches view him, but there is always time as Orthodoxy "re-discovers" many of its western treasures after some time of Eastern isolation. One only has to look at the explosion of interest in Celtic saints to see this in action. It is a great thing to behold, especially since saints like St. Martin of Tours, St. Hilary of Poitiers, St. Hubert of Liege, etc, all have such wonderful stories and lessons to guide us with.