Here's what I learned:
The bike
I commute to and from work (16 kms round trip) all winter, so I have an idea of what I'm in for. But I'm not going to use the cross bike a commute on for this race. On the advice of a racer from last year's race, who did use a cross bike, I've decided to ride a 26" mountain bike (no cash just now for a fat bike and, though I'm sorely tempted by them, I'm not certain yet), on which I have put the fattest tires I could find (2.65 inch downhills). They worked pretty well today. I had to get off three times, but for the most part I could ride over the drifts or follow the tracks of a whatever truck or tractor or snowmobile had gone before. I'm happy with the bike decision, though I'll have to adjust the set-up to get the right riding position. It's too upright for me.
Shifting
You have to be patient, and anticipatory, when you shift. Even when it's only -18'C, the shifter and derailleur are pretty slow to "click" into place. I've got some aerosol de-icer I'm going to spritz into the levers to de-grease them.
Goggles
I sweat. Even without a face mask, my goggles were frosting up at 4 miles. I didn't treat them with dish soap (which I definitely will), but I'm guessing it will be unlikely that I'll be able to use them for a full 20 kms. Either I'm going to have to slow down, and not generate as much heat, or I'll fog up.
Sweat
Damn. I just sweat too much, and I have this lie I tell myself, that if I'm not sweating I'm not working hard enough. It's a pain in the ass, really. And it's really not great for this race. I wore three layers today: a lightweight hooded polypro baselayer, a lightweight zipped fleece, and a uninsulated windbreaker. I was not cold, ever. By the end of this 20 kms the base layer was completely wet, and my thin skullcap and the baselayer hood were fused, by ice, to my sideburns (shave them off?) and it hurt to remove them (1st world problem).
Boots
I was sure that my ankle high winter-rated Columbias would be enough, if I wore good merino wool socks. This has just proven not to be the case. I believe it'll be Sorels for me. I'll take the straps off the traps, and still use the plastic pieces to help stabilize my feet on the pedals.
Gloves
Awesome. Thank you Farm Service for your super leather-palmed, unbranded, work mitts. No problems there.
Legs
Two layers was enough. Bike shorts (obviously), a mid-weight base layer, and then a wind-barrier front overlayer (also tights) was just fine. Not hot, not cool. I may put something over my left knee, which has some sensitivity issues due to a past injury.
All in all, I'd be fine with race day being a day like today. If I had a picture of the roads it'd look like snow drifts over a dirt road, and sometimes, just snow drifts, and no road. Good times ... sorta.