As much as I love IWRY, it pisses me off that after a few weeks Angel acted like he was the one who forgot and 6 months later he uses Buffy's words---needed more time before she could see him for cases because she was still in love with him and it hurt too much to be around him---as an excuse for not informing her of the fate of the only other person of her species (Slayers are just as much a species as vampires). "I was trying to save someone's soul. That's what I do here and you're not a part of that. And that's your choice, remember?" Sanctuary and later Cangel take away some of my enjoyment of IWRY. Buffy deserves better than the happiest day of her life being with a man who went on to side with her rapist against her and then got obsessed with one of Xander's ex girlfriends.
Becoming #2 works as a Buffy as Slayer episode as much as it does a Bangel one.
* Whistler.
Buffy correctly guessed that he was an immortal demon sent down to Earth to even the score between Good & Evil. In the comics it is revealed Whistler was the offspring of an Old One (pure blood demon) & a Power That Be and has precognitive abilities. In Intervention, Giles told Buffy the desert location she would embark on her spirit quest was "a sacred place near the Hellmouth." She wondered how something holy could reside near so much evil. He said there is "sort of an equalization of forces." Angel & Buffy have always represented balance. Vampire & Slayer, male & female, tall & short, broad & petite, brunet & blonde, rain & sunshine, darkness & light, sinner searching for salvation & suffering saint, months in Hell & months in Heaven, son (Connor) & daughter (Dawn), tai chi & yoga, First Evil & PTB, WC & WR&H, masculine AtS & feminine BtVS. Every way they differ complements each other. It's like how on Xena Warrior Princess there were two complete chakrams, one dark/one light, and when Xena merged them it created an even better chakram that could be split in half but still work. It represented Xena & Gabrielle (yin yang) and their relationship (soulmates).
* Buffy sending Angel to Hell.
She looks back at it as a defining moment of her life. Their love for each other both saved and damned him. Her first death was about the Way of the Warrior and proved she could sacrifice herself to fight evil, her second death was about the Way of Love and proved she could sacrifice herself not as a casualty of war but symbol ala Jesus, a gift to mankind. Buffy sacrificing Angel was the turning point. She chose what she thought would be an eternity of suffering, destroying the soul of the person she loved most, and it was the right thing to do. It was the most evil thing she ever did and one of the hardest experiences of her life and yet it was for the greater good. She needed to find that third solution in The Gift because she needed to believe in something better, you do not win against the Darkness by killing the Dawn (pun intended). She said as much in First Date, "You can't beat evil by doing evil." It only pushes it back underground for a little while. Evil needed to be cleansed, cured. She told her Spirit Guide, "Death is not a gift. If I have to kill demons to make the world a better place, then I kill demons. But it is not a gift to anyone." She was talking about violence and hate and despair. It is all Evil knows and she is on the same page as Gabrielle that "Peace is worth fighting for" but also like her, she gets that the opposite is forgiveness and love and joy and those do more than protect the world, they save it. If she hadn't of killed Angel she might not have reached the state of This Cycle Has To Stop and maybe would've let Dawn die and that would've reshaped the story too much. I love that she has the memory of being in Heaven for five months, that she became Queen of the Slayers, that the Hellmouth was closed, that she has the Scythe, that her journey as a hero got so epic and far reaching and affected entire universes and she became a major player instead of just a formidable warrior.