It wasn't bad, but I don't think it was as awesome as people think it was. It's funny how the rose colored glasses of nostalgia work.
The BeOS graphical user interface is clean and lightweight, but flexible enough for power users. Unlike Linux, BeOS is not based around the command line. And yet, BeOS includes a full bash 2.0 shell for those who want the extra power of the Unix shell. Again, "The grace of the Mac, the power of Unix."
That's a bunch of BS. You can run bash on any OS but that doesn't mean you have "the power of unix". Without a set of good command-line utilities a shell is worthless, just take a look at cmd or PowerShell on Windows.
Symmetric multiprocessing
The multithreading made things more responsive and it definitely made the teapot demo cooler but IIRC some bit of multithreading was required for every app so developing for BeOS was more complicated than other OSes. Most developers still can't get multithreading right, forcing it on them is only going to cause problems or scare them away.
Object oriented. Almost everything in BeOS is object-oriented, from the lowest levels to the highest. The system works on the principle of clients and servers, where clients are usually applications and the servers are system objects such as the media_server, the net_server, the app_server, and so on.
Ironically one of the things people are complaining about with Vista is that most of the video and audio drivers were moved to userspace, but somehow when more things were done in userspace in BeOS it was a good thing.
Not unique to BeOS in any way, even back then.
Database-like filesystem.
Sounds like extended attributes to me. And while on the surface they seem like a good idea and there are a lot of cool things that you can do with them most people ignore them because very few, if any, tools support them so you lose them very easily. And if you do something like copy the file to a FAT filesystem on a USB stick, email the file without putting it in a special container, etc you lose the attributes.
While it's still a checkmark in the feature column NT shipped with a POSIX layer back then too.
Support for alien fileystems.
Linux does the same thing, each filesystem driver is just a module and can be runtime loadable just like any other. NT has always supported IFS drivers that are similar AFAIK but the IFS DDK cost a pretty penny back then AFAIK so only corporations ever thought about it.
This is personal opinion, I'm sure people working on APIs like Win32, POSIX, SUS, etc would say that the parts they've designed were clean and easy to use too. And I'm also sure that if BeOS did take off it would have accumulated many layers of compatibility as more functionality was added, removed, moved, etc just like other APIs have over the years.
