Haven't seen anyone mention this yet ... It was low 40's (F) today and when I got in my car, there was a yellow dotted line in the regen area indicating regen was limited. I was quite surprised, for two reasons (as compared to the Roadster). 1) It wasn't on/off and 2) it had to be a LOT colder outside for the Roadster to disable regen (I realize we're not comparing apples to apples here -- on/off vs. limited regen)
Regen slowly increased and was back to normal within 10-15 minutes (I missed when it went back to normal).