After spending five minutes with it, I can tell you that it’s actually pretty nice. The animations are smooth, icons look good, and Samsung’s idea of things being more comfortable to look at actually plays well here.
Naturally, the big addition is the Night Mode, accessible via the Display menu in Settings. Once enabled, it darkens portions of the UI, though, I didn’t see an option for changing your accent color. Maybe that can be built in ahead of launch.
Other than that, you can see where Android Pie shines through Samsung’s skin, with plenty of rounded things being front and center, such as system toggles and pretty much every corner of the UX. I mean that literally.
Here are some photos, then head here to get signed up to try One UI on your own select Galaxy device.