I don't think I could ever play without a jetpack. Ingot density helps solve so many logistical issues. Higher tech recipes making some things more efficient gives the game a really fun sense of progression.
That's outside of just liking all the puzzles it adds to the game.
After 200hrs in my SEK2 run, I don't think there is a way to return to vanilla. I'm even thinking of doing another run after finishing this one.
At first I thought the progression takes too long and the logistics were complicate but after some planning and structure is really fun to solve the puzzles and see how everything works after putting the effort.
Has anyone played in multiplayer? I think it would be fun to plan production projects in group haha but none of my friends like factorio.