A few thoughts after doing a couple of playthroughs:
Really like the new prologue. Firstly, I like the setting because it's so relatable; seeing someone sitting alone outside a club, wondering if you should talk to them or if they just want to be left alone. The fact that Ian decides to talk to her, makes their lives tied together because of an active choice, not just because they keep bumping into each other at the start of the story.
That scene, together with the new pictures and inner monologue about Gillian, also makes their previous relationships more actively involved in the story. Though I feel we now should learn more about the actual breakup between Ian and Gillian at some point.
The rest of the adjustments in the first four–five chapters overall work really well too, I think (though it's impossible to keep track of all the changes). For the last few chapters Lena's been the one using Robert, not the other way around, and now that's more visible earlier in the story as well. That also makes it easier to follow Lena's logic when she's having casual sex with Robert, but waits to have sex with Ian.
I also wrote earlier that Seymour's path would benefit from being slightly more developed before the scene in chapter 9. I think their rewritten first photoshoot managed to do that, along with the fact that Lena can now think about how the shoot turned her on, and that Seymour's powerful position in the city is talked about more. She doesn't know what she's getting herself into before their meeting in chapter 9, but she knows more than enough to give her reasons to back off if she's not intrigued by the attention he's giving her.
Also really loved that Lena's friendship (and eventual potential relationship) to Holly isn't as dependent on Ian as before. And Stan's path works way better now. I'm not that interested in it, but either way he's now a coherent character instead of changing from chapter to chapter because Eva doesn't know what she's gonna do with him.
Billy: I'll reserve my complete judgement until we know more about the reasons for his change, but I agree it was a big WTF moment. I support it if Eva doesn't want two black characters who's basically there just because of the BBC kink. But if that's the case, it would surely be better to have a more varied cast of coloured people from the beginning, instead of changing Billy the way she did now. I guess we'll might get an explanation after the final version is out.