Roughly twenty years ago, maybe more, maybe less, I was on a visit to New York City, when the cousin I was staying with took me to some sort of PC club or users group meeting where they demoed BeOS. I have vague memories of a dimly lit room with the demo being shown on a projector, The presenter brought up an app which had a 3d cube and he proceeded to play a video on each face of the cube while rotating the cube. I can't remember how the sound was handled but, I remember being blown away by the fact that this OS was handling six videos simultaneously, each one being rendered on a face of this 3d cube that was being manipulated in real time. The hardware was a multiprocessor box of some sort and was probably fairly powerful at the time.
When I got my hands on my own downloaded copy of BeOS R5 Personal Edition, I installed it my own modest PC to give it a whirl and was blown away again by how fast it booted and how responsive it was. It made my modest PC seem very fast. I remember doing an experiment where I loaded multiple mp3 files and played them simultaneously I had so many files playing at the same time that I could barely make out a single one but I couldn't hear any glitches. Doing the same experiment on the same hardware running Windows produced audible glitches with only three or four songs playing simultaneously. I was hooked but, the Internet had become "a thing" by then and I was having issues with my dreaded winmodem (remember dial-up?) so, I only played around with it occasionally. In addition, there were far fewer open source apps available, Mozilla being one of the few major projects at the time.
Over the years I have grown to dislike Windows more and more for various reasons and adopted Linux (Ubuntu) as my main OS as a result, starting with the first laptop I bought back in 2008 (came with Windows 7 Beta, a.k.a. Windows Vista). Regardless of what I am running, Beos/Haiku is never far from my thoughts. I consider it potentially the best OS ever. I have a few devices that use Intel Atom CPUs and when running Haiku they are all responsive and pleasant to use. No "clicking and waiting" unlike Linux which can become very unresponsive at times. I don't use Windows often enough anymore to comment on Windows.
BeOS was about 15-20 years ahead of it's time. Tablets are pretty much what Be Internet Appliances were supposed to be. If the amount of open source applications available now, had been available when BeOS was being actively developed maybe the outcome would have been very different. I think Haiku still has a chance of making an impact especially on more modestly powered devices.