Notwithstanding my professed conservatism on things Anglican, I have not known much about Archbishop Thomas Cranmer, other than the usual things: hero of the Reformation, martyr, English prose stylist par excellence, slightly wobbly at the end of his life on what he did/did not believe. But now I am getting up to speed with the aid of Diarmaid McCulloch's superb, and impressively dense yet well told story of his life. (Currently at the point where Henry is about to die). Readers here probably read MacCulloch years ago. Some thoughts from me might serve as revision for you.
First, I had not appreciated how complex, how uncertain, and how controversial the progress of the English Reformation was through the period of Henry VIII's and ++Cranmer's joint presidency over the Church of England. At times the pathway between being burnt for evangelicalism or being burnt for catholicism was very narrow indeed. Cranmer himself narrowly avoided execution prior to Henry VIII's death. One reflection is that if ++Rowan Williams has read this book too (surely he has), then he must sleep well at night. Like Cranmer he faces ever shifting shades of opinion, and the prospect that overnight the political landscape of Anglicanism will change dramatically. There is no new Archepiscopal territory Williams is exploring through these years ... and he does not have to worry about being burnt alive. He can even proudly walk in public with his wife!
Secondly, I had not realised how far Cranmer travelled in his own theological journey, how long he held onto certain convictions before changing them, and how many times those convictions changed significantly (especially on the meaning of the eucharist). There is a sharp reminder here that to be a 'Cranmerian Anglican' is best done with a full knowledge of the range of possible forms of being Anglican which could be described as 'Cranmerian', along with a need to have reasons for being the particular form of Cranmerian which one is, (i.e. other than 'if Cranmer believed it, it is good enough for me.' That only raises the question 'the Cranmer of which year?'). On the one hand, Cranmer's journey in theology is something of a licence for Anglicans to change their minds as time goes by and reasons for doing so come to hand. On the other hand, Cranmer's clarity of expression of his theology is potentially helpful, and may set him apart from other Anglican theologians: 'I follow Cranmer at point X because he clearly sets out why X is true. No one else does this so well as he.'
Thirdly, it is clear to me (now!) that there never was a golden era in Anglicanism when all Anglicans not only believed the same things, but did so joyfully and without nostalgia for a different day and age. In any endeavour to secure the imprint of truth upon a human society the ideal is that all should freely agree to the truth. Taking just the Henrician period of Cranmer's reforming archepiscopacy, the most obvious observation is that the battle for hearts and minds was not won by Cranmer and his evangelical fellowship of courtiers and clergymen. They tried. They preached. Some even gave their lives in the cause. But they did not win all to their side. Not hard to be reminded that in today's controversies in the Anglican Communion it is important to attempt to win hearts and minds if some kind of security of establishment of doctrine is to be achieved. Conversely, without that security, we should expect that a familiar pattern in Anglicanism will continue: one controversy after another, though hopefully without the burnings.
But Cranmer is no less a hero for my better knowledge of his life. He grasped the revelation offered him concerning justification through faith in Jesus Christ and stuck to it. A true evangelical, if ever there was one.