There is a notable difference between Ultra and default High, though, I don't know if it is really worth using except for screenshots and the like because of framerate. I was able to run it on ACM city with a decent FPS, but it wasn't too smooth.
There is one bug, I don't know if there is anything you can do about it, but, you can't toggle between the new options and the default ones. I tried switching from Ultra to High, then back to Ultra and Very High, and the shaders reverted to classic Blockland Style. So, you have to set Ultra or Very High before you start the game.