We're at 7400 ft elevation with a very hilly community of narrow streets so get lots of opportunity to test the LEAFs in winter conditions. Some notes:
1) While the LEAF is terrific compared to other front wheel drive cars it still is a front wheel drive car. We add snow tires to one of our LEAFs for extra traction for braking and acceleration, especially up hills. In snow tires the LEAF pretty much drives nicely on any road that has 4" or less of snow accumulated. The range penalty with snow tires is about 10%, which is really noticeable on top of the cold weather range penalty. Which is why only one of our two LEAFs has snow tires - the other has regular all-season tires and keeps maximum range but isn't drive on days with the worst road conditions.
2) Eco mode is our default driving mode (our LEAFs are pre-2013 so don't have B mode) and this is important when on slippery surfaces since the regeneration keeps the speed down, especially down steep slopes. Of course, you lose that advantage when charging to 100%. OTOH, drive mode is really helpful pushing uphill through unplowed snow drifts, especially with snow tires.
3) Remember that the LEAF has the ability to turn traction control off - not all cars have this option and it is extremely helpful if you do get stuck. With traction control on, if one drive wheel has no traction at all the system tries to divert all power to the wheel with no traction - so you just stay in one place with that wheel spinning even if the other wheel is on a solid surface. If you ever get stuck in a snow drift try turning traction control off as one of the first options to getting unstuck.
