I have brewed at 0 deg F but I don't plan to ever try it again. Too painful, too problematic with the cooling hoses and just a general pain in the tushy.
Of course I have to add "brewing after an ice storm" to my should-not-do-list now too. I fell on the ice while moving my boil kettle off the burner on the Friday before Christmas. Drove my right knee straight down into the concrete (210 lbs of me and 50 lbs of boiling wort). I wasn't sure if I was going to be able to get back up after the fall. I froze to the ice covered ground and didn't have my cell phone with me to be able to call anyone for help. It has taken 2+ weeks to get back to, mostly, normal.
On the upside, I didn't spill a single drop of wort and the beer, now named "Knee Breaker Wheat", is in the keg and carbing nicely.
Be careful out there.