1. It is written by the god, the one and only Joss Whedon! This, in my opinion, tends to guarantee that its gunna be a great episode as he's so talented and his episodes tend to be the funnier or more dramatic ones.
2. I'm a big Faith fan so I'm loving any episodes when the bad girl comes back to wreak havoc!
3. I thought it was really well acted by Sarah Michelle Gellar and Eliza Dushku playing each other characters. They did it amazingly well and it made me feel like the actresses had switched bodies themselves because they did it so well!
4. Any excuse to see Buffy with curly hair and leather trousers being naughty!
5. Well I'm a bit of a Riley hater so loved it that Faith flummoxed Buffy's and Riley's relationship a bit!
6. Has some classic dialogue in it; one of my favourites is of course the scene with Spike and Faith in Buffy's body.
7. It's got some great interaction between Tara and Faith and also has lots of Willow/Tara goodness in it when they do a spell.
8. Even thought Faith screws with Buffy's life you still feel bad for her at the end when its apparent how much she hates herself and how she has no one left to turn to.
9. It's such an original and different episode, a great gem amongst some of the not so good episodes of season 4.