Although the order of preference may shift, there seems to be a general consensus when it comes to Buffy seasons. Season 1 is rough compared to the others, the back half of season 2 is ridiculously good, season 3 is the most consistent, season 4 has the best standalones, season 5 contains "The Body" and "The Gift" which overrides anything else that happens in the rest of the season, and most people prefer not to speak of season 7. But it's hard to get a gauge on how the fandom feels about season 6 as a whole. There are some who hate it with a fiery passion, but then there are also some fervent defenders of it. Season 6 isn't my favorite season of the show (my order would be: 5, 3, 6, 2, 4, 7, 1), but I'm in the fervent defender camp, because I absolutely adore it.
It seems like some people's thoughts on season 6 are colored by the narrative that it technically shouldn't have existed. "The Gift," the season 5 finale, was so perfect of an ending that many people jokingly say "Buffy ended with 'The Gift'" and pretend that the last 2 seasons didn't happen. Buffy had been killed off and The WB didn't want the show anymore, so many fans were already turned off by the idea of it continuing on UPN. But to me, the show justifies its existence the moment it brings Buffy back to life at the beginning of season 6. It's not so much the act itself -- once you know that the show is continuing and you figure that Buffy: the Vampire Slayer needs Buffy, it's pretty easy to then conclude that bringing her back will involve some sort of spell -- it's the implications that the act has. From the brief bits we get of the Scooby Gang continuing their slaying without Buffy, it's clear to see that they're doing relatively fine, so bringing her back is something that they do because they miss their friend. But what was done out of longing ended up being a really selfish act, when it's revealed that Buffy was in heaven and that she was actually happy. I can't stress how much I love that moment in "After Life," when Buffy tells Spike about the true nature of her being brought back to life. I think it's the boldest thing I've ever seen on television, and I remember my jaw dropping as I gasped and shouted "WHAT?!" once the gravity of the moment hit me. After all of the struggling that we saw her go through in the 5th season, she was finally at peace, and then her friends ripped her out of Heaven, forcing her to return to everything she had escaped. All of the responsibilities, all of the loss, all of the bills, all of the drudgery. All of it.
This reveal, and her determination to keep it from her friends, leads to alot of the resentment and listlessness she feels. The beginning of season 6 is all about keeping secrets. In fact, the first 7 episodes are an interesting little mini-arc to start off the season. As we all know, this is a Joss Whedon show, and in Joss Whedon shows, the truth always comes out. And it's unleashed in a big way, as everything finally stumbles out into the open in "Once More, with Feeling," an episode upon which every fan can agree. It has the gimmick of being "the musical episode," but what's most impressive about it is just how much plot is stuffed in there. Buffy's resentment about being ripped out of heaven, Willow using magic on Tara to make her forget their fighting, Anya and Xander's anxieties about their future, Buffy and Spike's budding romance, Giles feeling the need to let Buffy go -- all of those tensions clash together and explode near the end of the hour. It's an episode so monumental, that the rest of the season is spent dealing with the fallout of the revelations that occur in it.
One of the big problems that people have with season 6 is its middle section. After "Once More, with Feeling" it's hard for anything afterward to not feel like a disappointment, and on my initial run through the series, I do remember feeling like the middle sagged a bit. But looking back, there are actually only three episodes that I don't like. I hate "Smashed" and "Wrecked," and I was never into Riley and therefore wasn't big on his return in "As You Were," but aside from those, there's some strong stuff in there. I know I'm the only one who feels this way, but I love "Doublemeat Palace," so that, "Dead Things," and "Older and Far Away" is just a killer 1-2-3 punch. Listen, I think the Willow addiction metaphor is pretty weak, and the middle/end of the season takes a relationship I really adored in Spike and Buffy and sends it to very ugly places, but all of the good material elsewhere in the stretch outweighs those two problems. Plus, I could argue that the Willow storyline is worth it, simply because of where it ends up, and that Buffy's self-sabotage is a natural reaction to the pain that she's feeling.
Honestly -- and pardon me for making a blanket statement -- I think that people who don't like season 6 of Buffy have never been really depressed. I suffer from depression, and I watched the show while being at a particularly low point, so this season was some of the most raw and real television I've ever seen. Buffy may come off as whiny and mopey to some, but to me it's one of the best depictions of clinical depression on television. The unrelenting bleakness turns many people off -- and to be clear, it is an exhausting and unpleasant season to watch -- but when you're in a certain mindset it's easy to let the mood just envelope you. Another big gripe that people have is that there's a tonal inconsistency to the season, complaining that the usual goofier standalones don't mesh very well with the dark tone of the season. I call BS on that complaint too, as it displays a fundamental misunderstanding of depression. I was recently having a conversation with a friend of mine about how miserable I am, and she responded, perhaps disbelievingly "but you never seem that way when I see you." People who are depressed aren't incapable of happiness, and it's true that I'm quite a jocular person when I'm around others, but the season understands the nuance of the shifting emotions that come with mental illness. So episodes like "Gone," "Doublemeat Palace," and "Tabula Rasa" work for me in the midst of all the emotional turmoil.
Season 6 of Buffy puts every character through the grinder and by the end, you feel like you've been on a long, grueling journey with them. So when Xander talks Willow down at the edge of that cliff or when Buffy climbs out of that ditch her and Dawn got stuck in -- LITERALLY CLIMBING OUT OF HER STATE OF DESPAIR -- it's so freaking cathartic and oh my god I can't take it. There's so much pain in these episodes: the pain of losing a loved one, the pain of clinical depression, the pain of being betrayed, the pain of growing up and realizing that life isn't going to turn out like you hoped and dreamed it would. If you can't find the beauty in that, then I don't know what to tell you.