There's a reason FOX's Glee stays away from funk music most of the time. It doesn't go very well with the characters or tone of the series. Yet, in "Funk," the penultimate episode of the first season, funk music is smashed into Glee throughout the episode, regardless of the low quality of much of the resulting material. There's a reason the "Funk" numbers do not end the Volume 3 soundtrack, despite airing last. And that's only part of the problem with a mostly lackluster episode.
Perhaps the best, most interesting story happening in "Funk" is that Jesse (Jonathan Groff) returns to Vocal Adrenaline. His mission over, he must reintegrate back into his group. But the other members are suspicious, and test his loyalty, even making him crack an egg on Rachel (Lea Michele) to prove it. Given that Jesse undertakes the assignment to go to McKinley in the first place shows his level of support for his director and the group. So it is no surprise that, despite his feelings for Rachel still being present, given the expressions on his face, he does what he needs to to re-win the trust of his classmates.
This is cool, because it gives some depth to Jesse. The face of the villain, Glee fans have gotten to know him these past months during his tenure at McKinley. As such, it's easy to care about him and his feelings. The test of Jesse's character comes in returning to Vocal Adrenaline at all, considering that buzz is the New Directions are poised to topple their reign. If Jesse were just a selfish jerk, he would stay at McKinley and take the win, with no regard for where he comes from. That he goes to such lengths to go back, and to prove that he's one of them, shows that Jesse is someone who has character, and who cares about his glee club.
Though, it is hilarious to see his dispassionate "I'm so depressed" following his teammate's declaration that they are "soulless automatons" at the end of the episode!
Rachel is upset, of course, not seeing why Jesse is doing what he's doing. If she were privy to his motivations, she'd probably forgive him, and help him do what he needs to do. Instead, she talks of feeling betrayed. This reveals that Rachel doesn't care as much about Jesse as he does for her. While he does choose his group over Rachel, were their positions reversed, he would probably stand by Rachel as she humiliates him for the sake of her group. Instead, she abandons Jesse, not even giving him the chance to explain himself. So Rachel is as selfish as she is so often accused of being.