I'd love to know what BeOS did to achieve those magical-feeling results, and why it hasn't been copied by everyone else. I reckon it's gotta have a lot to do with process scheduling and how UI events are dispatched, but if it's mostly those couple things, why isn't every modern OS doing what BeOS did? There must have been trade-offs I guess but from the user's perspective it seemed to be 100% an improvement over everything else—it's not like multimedia took a backseat to user interaction, or parts of the UI lagged so others could feel fast, everything felt smoother, quicker, and more responsive. On single core machines with 1/16 the memory it takes to start Slack, too!