The 6809 had some hobbyist/consumer prominence on this side of the pond in the TRS-80 CoCo - and some European similars. And there was a multitasking OS written for it - OS-9.

OS-9 has an interesting history in its own right. It was ported to a wide range of subsequent architectures. All sorts of applications - Fairlight synths, Philips CD-i, most of the traffic lights in the US in the 80s and 90s to name a few.

The 6809 was used in a production gadget, the Vectrex, the only vector-graphic consumer videogame console. It came with a screen that worked like an oscilloscope -- no raster, just an electron beam sweeping along the line. So, no jaggies.

As it was necessarily monotone, games came with clear plastic color overlays for the screen.

6809 was notable as the first 8-bit microprocessor with a multiply instruction: 8x8->16 bits.

I never got to use the 6800, but did use both the 6809 and 68000 in assembler. Both were a joy to work with.

The 6809 was an answer to the 6502. They needed something reasonably “better” than the 6502 to justify the price tag. Unfortunately, for them, the 6502 and it’s variants were too entrenched at that point.