From "A Sense of the Ending: Schrödinger's 'Angel'" a literary essay by Roz Kaveny, published online and in "Reading Angel : The TV Spin-off With a Soul" edited by Stacy Abbott:
".... In Angel, the character who has most consistently acted as Angel’s shadow and surrogate is Wesley, whose story has throughout been that of ‘The Man who Learns Better’. Remembered by Angel and the audience as the largely useless fop of Buffy Season Three, the ex-Watcher has re-invented himself as a leather-clad rogue demon-hunter without having changed his essence. The ways in which he changes are many and varied: to pick but one, he consistently chooses Angel over earlier loyalties to the Watchers’ Council, even when what appears to be his father arrives claiming to be its emissary (‘Lineage’, 5007). Wesley is a character whose essence is to lose and yet lose so honourably as to be admirable. He is the ‘loyal servant’ who betrays Angel by kidnapping his son, but does it to save him from the prophesied guilt of killing him – and in the long run, Angel has to kill Connor so that he can be reborn as the sane heroic youth of Season Five. Wesley sells his own soul to Wolfram & Hart in a vain attempt to save that of Lilah, whom he no longer loves; he finally wins Fred, only to lose her to Illyria; and it is his death that finally redeems Illyria by teaching her the meaning of human grief. Wesley’s death is both the price of Angel’s victory and a demonstration that the mission is about self-sacrifice."
".... ‘You’re not looking at your friend; you’re looking at the thing that killed him’ (Giles in ‘The Harvest’, B1002) is even truer of Illyria than it was of, say, Harmony; Illyria is a long dead god/demon that inhabits the corpse of Fred and devoured her soul in the fires of her re-creation. Yet, as with many vampires, it is not as simple as that; even before the restoration of Fred’s memories of her penultimate year and a half of life she is totally Illyria, yet increasingly conjoined or contaminated with elements of Fred. If Illyria were wholly and solely the creature she claims, and believes herself, to be, she would not impersonate Fred for the dead woman’s parents, or offer to give Wesley a final perfect day. Both Buffy and Angel have always been shows about redemption; the reason why Wesley refuses Illyria’s offer and then accepts it when mortally wounded is not that he dies having finally chosen illusion over reality, but that her offer is an outward sign of genuine inward change. In an interview at the Hyperion convention, Amy Acker said that Joss Whedon redirected the scene having realized that it was not about Wesley’s love for Illyria or Fred, but about Illyria’s love for Wesley."