First, I'm somewhat surprised by the lack of response to the new preview, both here and on Steam. But oh well.
I was looking forward to this, and the video looks great. However, I experience a crippling loss in performance using the new preview. I run Win7 64bit on a three-year-old ASUS gaming laptop with an Intel i7 CPU and GeForce 765M GPU; both Windows and GPU updated with the latest updates/drivers. While perhaps not optimally set up, Alpha 18 yields ~47 fps (measured with the in-game fps counter) in the standard solar system simulation, which is smooth enough. Less content-heavy sims run much smoother, with only sproadic short fps drops during multiple collisions for example.
However, the new preview A) yields ~27 fps officially (which would be tolerable, and understandable due to the updated graphics) but B) only yields very few effective fps in the simulation of the planets' orbit. The in-game performance test showed an average of 67 fps last night, but both the test simulations and everything else points to some kind of problem displaying it properly.
Here's a video showing the result (it's
unlisted so can only be accessed with this link):
https://youtu.be/KdF3xQaisxsAny input is most appreciated.
Edit: For comparison, here's how Alpha 18 runs the same sim:
https://youtu.be/WYHqrvXhJSc