The fourth beta for Haiku R1 over a year and a half of hard work to improve Haikus hardware support and its overall stability, and to make lots more software ports available for use. Over 400 bugs and enhancement tickets have been resolved for this release.
Source: R1/beta4 - Release Notes
This is pretty impressive, but considering BeOS was niche to begin with and that it has taken 20 years to get to Beta 4… well, I just wonder why this would be used for more than just nostalgia and to play with. Perhaps I’ll be surprised?