I have a One, but only because my prior “pen” died. The 1-second read time is not a giant improvement over 2-3 seconds, IMO. No one’s that busy.
One theortetical advantage of the speed is that you COULD more easily understand delta t’s at various depths within, e.g., a roast, without poking multiple holes.
In my use the MK4 was an excellent upgrade from its predecessor but the One is only a minor upgrade to the MK4. The timing improvement is only modest to nearly undetectable in most of my uses.
It was a Taylor. I think it was the “Connoisseur Turbo Read” 9867B. I was happy with it, and actually preferred its ergonomics to my Thermapens. It worked great for >10 years.