The FM is what got me started in photography back in 1978. It served me well for 20+ years, shooting slides and film. I finally traded it in on an N70 that I still have but haven't used since I went digital with a D100 way back in the early 2000s. I still have a little bitty regret in getting...
I haven't shot many at 12,800, but here's one. I wanted to get a photo of the truck that had crashed, only had my 24-70 and it was dark. Slight NR in LR6.
But I have shot a number of pics at 6400 and they're pretty clean....
Even with my relatively new D750 (4/15) and it's awesome ISO capability, I still find myself shooting wide open on all of my lenses (except macro) at some point and wish there was more room to open up. Not for bokeh's sake, but to get the exposure (without flash). I'm sure I could get used to...