Nice summation.
I would add that maintaining a very smooth and steady cadence also helps a lot. Which leads me to thought number two—if you are riding a geared-bike make sure you shift into the proper gear early so that you can maintain a steady cadence, don’t have to get out of the saddle, and have time to deal with any snow/ice/mud-related derailleur issues. Definitely shift down if you decide to hop off the trail to go around any really slick spots or you’ll bog.
As an aside, I actually had much better control in the snow yesterday on my winter fixie than on my cx-rig last year. And clean up was ridiculously fast and easy. Might have to put the cx-rig out to pasture.
Good luck out there, everyone.