My gasoline B4 Espar has been working great. Haven't been in the extreme cold that you guys are dealing with. Coldest I've used it is about zero, and it got so hot that I needed to open my roof vent. I don't think my digital thermostat is very accurate where I have it located. I can turn it down to 60 degrees and it still gets way too hot to sleep.
It's 65 degrees here right now, but it gets down into the upper 30's at night. Maybe I'll try unplugging the digital thermostat and let the Espar default to the internal unit heat sensor.
And I bought the gasoline Espar because I'm staying with gas engines and plan to move it to my next van.
I have the old thermostat....not digital...it is more of a guideline thingee....depending on wind direction and degrees....what was good one night will be too high or too low the next...you'll get used to it after awhile...