What I'm wondering at this point... If I buy Odyssey and upgrade, will I have to download it again? Or will my current 4.0 Horizons just unlock into Odyssey?
As to impressions of the 4.0 demo... Even on my older system, the 4.0 Horizons "Odyssey demo" is not terrible. My choice at this point in time is either stay on 3.8 (or maybe even just call it done), or buy Odyssey. Seeing 4.0 in action, so far I could live with it without a PC upgrade.
Yes, performance is the worst of any game I have ever played on my PC. Landing on a planet, at a station, fleet carrier, or even a little space outpost will bring my performance down from 60fps to 30. The new surface outposts are in the 15 to 20 fps range. Sometimes the planet surface material scatter remind me a bit of Playstation 1 pixelated textures when viewed from altitude (it's not the textures that are pixelated, it's like the "pixel" effect is due to the pattern used to arrange the higher res textures).
My Galvanized SRV paint job is no longer metallic effect, just purple. My "Odyssey" Dolphin paint job has cool chrome and black trim lines in 3.8, but it's just flat dull gray in 4.0 and that's sad.
With medium settings, lowering my resolution from 1080p to 1280x720 (or using the FSR mode) can actually keep me above 50 fps on some planet surfaces, even with the Planet Surface Work slider to the right a good ways. Of course, this means things look like 720p does. Shimmery. But I am actually a bit surprised that my old GTX950 2GB card is doing this well.
On the plus side (for me) so far the UI is not as bad as I imagined. No problems with UI during a few ship transfers, outfittings, and traveling around 2,000 LY out to see the Thargoid Star in person.
But so far, I've liked a lot of what I've seen. Little visual things here and there. The FSD jump sequence is nicely done. The solar prominences are far better.