My C= experience started and ended with early Amiga. I had an A1000, and a friend an A500. We mostly played games but also I ran a BBS for a while (Citadel 68K, it read the whole message database into ram and did all reads from that. Only writes went to the floppy).
I have no nostalgia feelings for the C64, C128 etc machines. I have an Amiga emulator I fire up about once a year to noodle around in and that's about it.
The Callback phone does not appeal to me because I never was into the C64, but it does appeal to me because for a while about 5 years back I switched my sim over to a Nokia dumb phone to see if I could get by without all the iPhone conveniences. That didn't last too long.
I'm sure Callback will find it's niche users though. Good for them :)