ItsJustMe

I'm thinking about buying/building a new commuter, and internal hubs are a possibility.
I ride year round, so far in temps down to -25*F, and in Michigan quite a few weeks are spent right around freezing, so I ride home in slightly above-freezing conditions, getting slush and water and dampness in everything, then the bike sits in the garage while the temps go down to 15*F and all that water freezes solid.
Several times a year my rear derailler will be frozen into one gear. Sometimes I can work it loose, sometimes I wind up going all the way to work in one gear which adds significant time to my already-longer winter commute time.

My question: How do internally geared hubs do in very cold temps, like down well below zero? I've searched here and people say most of the trouble is with the cables themselves freezing up, but I'm not sure I've read messages from people who have used the IGH in REALLY cold temps; most people are saying 10 or 20 degrees F, which isn't really cold.

So, do IGH do well or not? Also, how about Shimano vs SRAM since Shimano uses grease and apparently SRAM uses oil; does the thinner lube help SRAM work better in the cold?

Just to save time, single speed isn't an option, so don't bother suggesting it.