We actually now refer to this holy day as the Feast of All Faithful Departed, in part because Anglicanism does not carry a theology of purgatory as does the Roman theological foundation for this day. I regret that I have lost the source for the quotation below, coming as it does from an old notebook, especially as it is the most succinct appreciation of today's theology that I've ever found.
"Whether or not one should pray for the dead is one of the great arguments which divide Christians. Appalled by the abuse of indulgences in the Church of his day, Martin Luther rejected the concept of purgatory. Yet prayer for a loved one is, for the believer, a way of erasing any distance, even death. In prayer we stand in God's presence in the company of someone we love, even if that person has gone before us into death."
O God, the Maker and Redeemer of all believers: Grant to the faithful departed the unsearchable benefits of the passion of your Son; that on the day of his appearing they may be manifested as your children; through Jesus Christ our Lord, who lives and reigns with you and the Holy Spirit, one God, now and for ever. Amen.