Who Are You? is an outstanding episode in all respects- the writing is fantastic, the fights are amazing, the storyline is gripping and the acting is absolutely incredible. Definitely a series classic, this embodies most of the reasons I love Buffy.
First of all I'm starting by saying that Sarah and Eliza were phenemonal in this episode, nothing short of perfect. Both played each other's characters so fantastically- Sarah played Faith's emotional and complex journey perfectly and Eliza was brilliant portraying Buffy on the run. Eliza was a bit better as Buffy but when you add to the fact that Sarah is playing Faith acting as Buffy, they're even. The starting scenes in the bathroom were hilarious with Faith playing around with Buffy's body, getting comfortable. The bit in front of the mirror were especially brilliant with Faith screaming "You can't do that. It's wrong!" at the mirror and playing a better-than-thou Buffy, which is what she perceives Buffy to be.
The Faith scenes were the real highlight of the episode and it was a joy to see Sarah playing her, even just for the novelty value. The speech she gives Spike at The Bronze is unforgettable and really showcases the amazing chemistry between Sarah and James- as enemies they're brilliant but they're even better as lovers. They work together so well and it's one of the starting points with Spike's infatuation with Buffy.
The showdown at the church was very memorable- I wish it had been a little longer but it was still awesome. Seeing Faith break down, screaming and punching Buffy, yelling at her own body "You're a disgusting, murderous b!tch, you're nothing!" was a really shocking and emotional moment, where we see that Faith isn't self confident as she makes out but really hates herself. It is played magnificently and watching her say to the vampires at the church "Because it's wrong" is a massive step forward for her. However, the Willow/Tara scenes aren't to be overlooked. First of all, Tara is awesome for recognizing Buffy isn't Buffy immediately and you like her way more just for that alone. However the spell scene was a big step up for their relationship- it's obviously a metaphor for sex but seeing as the network probably wouldn't have allowed it at the time, magic is the next best thing. It is a very sensual scene and marks the real turn for Willow and Tara into something more than friends.
The Buffy/Riley scenes again don't interest me. I can see why Buffy may feel all betrayed that Riley slept with Faith-in-Buffy but come on, he can't be blamed! Their drama really does nothing for me, so I tend to not pay attention to them.
The end scene with Faith on the back of a lorry or something to L.A. was a perfect ending. It rounds off her arc on Buffy while also setting it up for the Angel episodes "Five by Five" and "Sanctuary".
Who Are You? is nothing short of spectacular; action packed, moving, shocking, magnificently acted and just plain fun most of the time. It isn't an episode that should be missed.