This movie was surprisingly good. After having seen the Deen adaptation of the Fate route and the Ufotable adaptation of the UBW route, I considered F/SN a very enjoyable but not that well-written series. What I didn't expect was the Heaven's Feel route to have such a refreshingly interesting conflict.
My main issue with the other two routes was that, while Shirou was constantly talking about how much he wants to be a Hero of Justice or whatever, he never actually had to truly prove it. Sure, he had to fight a lot of tough opponents, but fighting bad guys is not exactly challenging to the moral burden that comes with wanting to be a hero. Heaven's Feel challenges Shirou's goal more than ever before, as he has to make a very difficult moral decision this time around: Either kill the girl he loves, or watch her slaughter countless innocent people. At the end, he cannot bring himself to kill her, and now he has to pay the prize.
While the answer may seem obvious (one life is not worth as much as the life of countless other people), the act of actually killing a person, one who is a victim at that, is a really difficult task, and therefore Shirou's moral struggle is completely understandable. This movie and the one that came before also do a good job at establishing the relationship between Shirou and Sakura. The love between the two is somewhat based on pity, as Sakura is a very victimized girl who had suffered her entire life and has a monster inside her that she cannot control. It feels natural that Shirou wants to help her, which even results in them having sex after Sakura asks him. F/SN is based on a visual novel and thus had originally a bunch of obligatory sex scenes forced into it to help its sales. The moment they have sex in the movie though feels completely natural and not forced at all. It serves the plot and most importantly the characters. I also really like how Shirou tries to block out the fact that Sakura is turning into a monster. He clearly knows what's going on, but he's not emotionally ready to take responsibility. It makes him all the more human.
Another thing that works for me so far is the whole horror aspect. It might be because of Ufotable's presentation, but even just the thought of the servants being completely helpless is scary in its own right. In the other routes they are these juggernauts of destruction and as long as a human had a servant they were pretty much safe for the most part. They were reliable guardians. But in this continuity, not only are they helpless against the dark matter, they are also turned into zombie puppets that are then used against the main characters. And the main characters can't even really use their own servants to contest them, because they will also just get swallowed up by the dark matter and turned into bad guys themselves.
I also like that the whole concept of the holy grail war gets turned on its head and the participants now have to deal with it. Because let's be real here, the holy grail war is basically a sport. Few of the participants have a good reason to hunt for the grail and most of them just do it for the thrill of battle or to earn bragging rights for being the best mage family or whatever. Nice to see how their stupid death game backfires right in their faces. It also adds some tension how things aren't going as planned at all. In Fate/Zero, there were also some disturbances with Caster disobeying rules, but it never felt like a huge threat, more like an annoyance. In this movie, all the grail war rules are basically turned off and it's not about competition at all anymore, it's just about survival and somehow stopping this threat before it's too late.
Despite all the praise though, there are still a lot of things I don't like much, and it mostly comes down to the usual F/SN problems: Overreliance on edge (especially Shinji is as charming as usual), stupidly over the top battles that go on for far too long and consist of lots of "firing mah lazor", ridiculous plot-armor for certain characters, characters not always acting how they should (seriously Shirou, you're not worried about Saber's disappearance at all?) and some other questionable scenes (Archer can just... give Shirou... his arm... ok). Some things also aren't explained yet, especially in regards to the old Matou guy and his assassin servant. The third movie will be the deciding factor there, but it will need to come up with some good explanations. And lastly I'm not the biggest fan of the way the movie ended. Like I get it, Sakura wanted to protect the others by leaving, but going to her old house where Shinji is? That was obviously a dumb choice.
But besides all this, I'm pleasantly surprised with this movie and I'm very excited for what's going to happen in the next one.