13" i5, no problems since update to Mojave.
On High Sierra I had a few freeze+restarts, but not sure whether that was the OS or Safari (they all occurred when using Safari, which may be coincidence). I switched my default browser before updating, but not long enough before to be sure whether it was the update or change of browser that fixed it. At some point when I'm a bit less busy I'll try Safari again to see.
No problems with keyboard, heat or any of that stuff.