You guys have pretty much covered it, but will add my experience in Montana. Prior to the Minimax, I had a 7.3L PowerStroke for ten years, and dealt with plenty of cold weather. First, as has been said, depending where you live, fuel stations switch to a winter blend #2 diesel sometime in the fall and switch back to summer straight in the spring. For us, it's October and April.
I've never had a problem with gelling of #2 winter blend anytime it's been above -20F, and that's with my truck always parked outside. No additives required.
#1 diesel has an even lower gelling point, I believe somewhere around -35F. If the forecast showed lows below -10F, I usually went ahead and pumped some #1 in there. However, right before we traded the 7.3 in, we had several -20 nights where I only had #2 in the tank, and had no problems. Of course, I had the block heater plugged in to help the big beast turn over, but that block heater does nothing for the fuel lines running from tank to engine.
If #1 isn't an option, you can add a winter-specific diesel additive - almost every fuel station, WalMart, or auto parts store has it. And finally, if you are on the road and it seems as if the fuel may be gelling, there's a specific product called Diesel 911 that rapidly breaks down gelled fuel. The engine still needs to be running for it to work, as it needs to make it through your fuel lines.
We've had a very cold winter so far. The 2.8 has been mine for 1.5 weeks, only with #2 in the tank, and has done just fine down to negative teen temps. I must say I love how well the truck starts cold - zero smoke is amazing considering the freight-train smoke that accompanied starting the 7.3.