(Comment on https://hackaday.com/2021/10/27/vcf-east-2021-preserving-heathkits-8-bit-computers/.)
My H8 was hooked up to an H19 terminal and H17 floppy drives, so the experience was similar to using a TRS-80 or an IBM PC. On HDOS there were Microsoft BASIC, the less capable Benton Harbor BASIC, lots of video games using the semigraphics character set (and the H8’s built-in speaker), text editors called PIE and SCRIBE, text formatters similar to nroff called TEXT and RUNOFF, and text files traded on disk at user-group meetings, including porn. For electronic engineering, you could do a lot of calculation and simulation in BASIC that would have been really hairy on a programmable calculator, although its ability to plot graphs on the screen was pretty limited.
I was a kid, so my favorite use was the games (and the porn). My favorite games included Munchkin (a Pac-Man clone), Invaders, SEABATTL, A Remarkable Experience (a puzzle-solving text adventure similar to ADVENT or Zork), CASTLE, and Star Trek, where you would fly around shooting Klingons with your phasers and photon torpedos and try not to fly the Enterprise into a star. Other games I played included Lunar Lander, Hammurabi, Towers of Hanoi, Reversi, chess, and a significantly enhanced non-turn-based version of the "robots" game in the bsdgames package.
Under CP/M there was WordStar, a mostly WYSIWYG word processor with only a few nroff-style dot commands left, and SuperCalc, a spreadsheet. There was a huffman-coding utility called SQ[ueeze]. Later I installed MODEM7 under CP/M and dialed up BBSes with a modem, and I could upload and download files with XMODEM. Sometimes, though, I couldn’t download a file unless the BBS sysop was kind enough to break it up into pieces that were smaller than the (100KiB) floppy disks.
Despite the availability of PILOT, effectively everything that wasn’t written in BASIC was written in assembly language; both HDOS and CP/M came with an assembler, a linker, and a library facility to pull only the library routines you needed out of a library. Later on BDS C and Turbo Pascal brought high-level languages to the platform, but they were too late and not competitive in performance with assembly language or beginner-friendliness with BASIC. Unfortunately, I never learned how to program in assembly.