I remember when I first hear about the relationship with NeXT and BSD; and decided maybe their operating system had a chance of being useful. Wow, that was a long time ago.
@Terry Poulin I remember my first time with a NeXT Cube.
Sexy as hell this machine. Was the reason to buy a g3 macbook a long time ago and hope that OSX will be the choosen one.
OSX wasn't the choosen one and Apple changed from the great PowerPC to Intel and I sell my Apple. LOL

Later on, I tried freeBSd again and again, building Firewall with OpenBSD. In the end, I just used Debian, Slackware and now Fedora.
@Christian M. Grube thanks to work, I’m usually found using Linux these days but it was FreeBSD where I learned how everything works. I was the kind of freak who abused /use/src to do things like tracking how the boot process goes from hitting the MBR to running Getty/login, and studying how standard libc functions were implemented.
@Terry Poulin On my side it was AIX since 4.2. Loved it. Some OS/400, but as much as I wanted to.
Two weeks ago I brought two full working IBM RS6K to the recycling center. No one would like to have it and I couldn't move it to my new homebase.
Sad moment
Never had the opportunity to try AIX, but seems like one of the nicer commercial Unix systems that’s still out there.
@Terry Poulin Far better than HP-UX.
I hated the HP Workstations, they takes ages to boot up.
At Daimler I moved them from one location to another. Time consuming as hell. With IBM, I never ever had a problem like the HP-UX machines.
Some used CDE as DE on AIX, I used E16. IBM made a lot of Tools, WMs, DEs available over FTP for their Unix. IT's widely used for CAD workstations.
CyReVolt mastodon (AP)
The odd part is that it would be okay because we do have replacements in place. :)
It's good to have a backup plan. Mine is FreeBSD for systemd/Linux.