OS-9 was a gateway for a lot of good developers. Constrained (8/16-Bit) enough to make you think but having a lot of the tools and ideas from mainframe/Unix world.

It was part of the strange CoCo experience. The CoCo had a superior CPU in that the 6809 was a great target for conventional compilers (as opposed to the 6502 which would drive you to virtual machine techniques like UCSD or Wozniak’s SWEET16)

Yet the 32 column text size was worse than the already bad 40 cols common on micros. It did not have the great audio of the C64 but the shack sold numerous upgrades like the Orchestra 90, you could even pack in four upgrade cards with the multi-pack. It was insane how many upgrade you could buy (like a digitized tablet, many kinds of dot matrix and letter quality printers, speech synthesis oak). Disc drives cost more than the Coco but they were way faster than the affordable 1541 that C64 users had)

I had a DEC printing terminal (with an acoustic coupler modem on the side!) and a TRA-80 Model 100 attached and could log in with three user sessions. I had a UART for one serial connection, the bit banger was fast enough for a printing terminal!

My Coco 1 starting burning up power supplies so I got a Coco3 which had 80 col text and a real windows + mouse experience for OS-9 but the third party software situation was terrible so I got a 286 machine in 1987, a time where I see Byte magazine is overrun with ads for PC clime builders. I got the money from a consulting project I did, I was told years later how much value my project made and should have asked for enough money to buy a 386.