gear, lenses, preferably L quality because they tend not to be phased by cold too much, should be fine as long as you give them a good half hour to adjust. rapid heating/cooling may cause water to condense, and that would be bad. i also suggest getting some underarmor gloves (not really needed so much for mkiii, but smaller cameras benefit from thinner gloves), put those under some thin gloves and you're set for an hour or more in -12C weather.
I don't hate macs or OSX, I hate people and statements that portray them as better than anything else. Macs are A solution, not THE solution. Get a good desktop i7 with Windows 7 and come tell me that sucks for photo or video editing.
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