It's not as good as the TV series, but one expects that from anime movies. Importantly for an Utena film, it's even more bonkers, making zero compromises and isn't just trying to rehash the same old story. Instead it's taking the same characters and themes, inverting some of them and telling a different story with them.
Think of it as a parallel universe version. Some fans think it's a sequel, although you'd have to force your brain into scary contortions to agree with that. Others think it's set in the afterlife, which is a more defensible reading.
On the face of it, the set-up's the same. Tenjou Utena in boy's clothes has just transferred to Ohtori Academy and gets involved in duels for possession of the Rose Bride, Himemiya Anthy. The sexual angle is more explicit, but that's okay. The TV series was doing the same. It just went about it more gradually, having 39 episodes to build up all those subtle references into something disturbing. The film does things that the TV show didn't (Himemiya openly offering her sexual services, Touga as a small boy apparently being sold into paedophile sex exploitation), but that's mostly just the movie not being able to do slow build revelations in the same way.
Mind you, the movie does have a lot of nudity. It verges on the gratuitous, even if it's defensible on artistic grounds as there isn't a stylistic element here that hasn't been pumped up to eleven. Do you want to be paying attention yet again to anime's mysterious reluctance to draw nipples?
It's not newbie-friendly. You'll want to be familiar with the TV series. The plot's confusing and impressionistic, characters are introduced casually (if at all) and the last act goes even further into surrealism and metaphor than the TV show did. You'd think they were expecting the audience to know the show already, except that they try to make a minor revelation (very early on) out of showing that Utena's a girl under that hat. I'm not saying it would be impossible to watch this film as a newbie, but you'd probably want repeat viewings to work it out. This is a film that fights tooth and nail against the casual viewer and it might well seem impenetrable if you're not watching it as an alt-universe spin on a story you already know.
The big difference is in the lesbianism. Both story iterations are ultimately about Utena having to choose between boys and Himemiya, but the TV show did this by making Utena fall in love with a boy while her marriage to her wife was ostensibly chaste. (Forget the symbolism, if you can. On a simple plot level, the story wouldn't work if Utena was shagging Himemiya because then she'd have been cheating on her with Ohtori and her emotional dilemma wouldn't work the same way.)
The movie inverts that. Utena has a past relationship with Touga and some emotional issues about that. We still have princes, phallic objects and symbols of masculinity (e.g. cars, swords), but they're abandoned, dead or useless. "A car without its key is stuck and goes to rust." Utena isn't just dressed as a boy at the beginning, but we're supposed to be thinking she's one. However that's before she and Himemiya go to the red-smeared temple that's a girl's special place, where they take off each other's clothes and find special intimacy. (Yes, that really is in the film, although I boggled at the ostensible literal interpretation of the scene, i.e. that Himemiya was intending to give a nude life drawing of Utena to their art teacher as schoolwork.)
Princes are dead. Magic castles are dead. Fairy tales don't exist. The movie has a motif of modern technology that was absent from the TV series, c.f. video tapes, the car chase, that glimpse of what looks like a post-apocalypse world, etc. The Kashira-Kashira Silhouette Girls are still here, but as radio presenters. Mind you, the movie's view of the modern world could hardly be called utopian, e.g. the locust cars.
On a more superficial level, the art and animation are heightened and more detailed. It's a movie. Production values are far higher. It's also even more abstract, as with the Ohtori Academy no longer looking like anything that could possibly ever have existed and instead resembling modernist art. Oh, and the hair. The hair, the impossible hair! The music sometimes pays homage to the TV show, which I loved when they recycled the title theme. It obscurely pleased me that this version also began with Wakaba, of whom I'm fond, but Nanami only appears as Cowbell the Cow in a fantasy sequence.
I'm not wild about Utena's look early on, mind you. It's unflattering. However her appearance is clearly a key element of her metamorphosis over the course of the film.
It's completely off its nut, but that's okay. It's Revolutionary Girl Utena. However, at the end of the day, I wouldn't recommend it to normal people, whereas I would recommend the TV show. The latter works better on a simple entertainment level. The movie is an art film par excellence and you'll sink without trace if you're not prepared to cut it a lot of slack. It's striking and memorable, but I think it would have washed over me a bit if the characters hadn't been fresh in my mind from watching the TV show. It's still amazing, though.