I really enjoyed Supersymmetry and found it to be an excellent character driven episode and loved that we got to explore new depths of Fred and see different sides to her.
I really liked the fact that Fred was sent to Pylea through a deliberate attack. It's bad enough that it happened by accident but when you learn someone you looked up to and trusted sent you to a hell dimension, you're going to be pretty upset. Or in Fred's case turn into a homicidal maniac bent on killing the man who ruined your life. Excellent.
Amy Acker was truly superb here and was genuinely frightening in some of her scenes where she's bent on killing Professor Seidel and the line "No. He's gonna die" creeps me out to this day. This episode is also the beginning of the end for Fred and Gunn's relationship as one of the things Fred loves about Gunn is destroyed; he has it in him to kill a person. The final scene where they're completely uncommunicative shows the direction their relationship is taking and that it's not a good one. Wesley and Lilah's relationship also takes a downward turn here. He's obviously still smitten with Fred and despite her later insistence she isn't jealous, the scene that she follows him to Fred's lecture and looks at him angrily proves otherwise. He also turns her offer down to see Fred's lecture. Wesley is still in love with Fred and his part in helping her kill Seidel proves this. He also keeps throwing out hints that Gunn isn't here for her in hopes that she'll get rid of Gunn.
The Cordelia and Connor scenes were.. yuck. Seeing Cordelia, the closest thing to a mother Connor has ever had, kiss him is all kinds of wrong. Thankfully she has amnesia or I'd be put right off her. I liked that she eventually went back to Angel though. The fact that even though she can't remember him but is still very drawn to him is proof that they were more than just friends. Cordelia herself asks if they were in love at the end here and we finally get the answer next episode!
Supersymmetry is an excellent episode that focuses on all the couples of the show and shows that basically all of them are taking downward turns. It provides us with more insight into Fred and shouldn't be missed.