My Christmas day exercise while everyone else was hiking around the park was me riding my bike down to Badwater and back. While Badwater is definitely lower in elevation than Furnace Creek, it's not very downhill. In fact, the constant rolling hills the road followed meant I accumulated about a thousand feet of climbing int eh 18 mile ride here.
While the weather was absolutely stupendous, the traffic was not. It was constant. Christmas time is by far the most congest of the year in Death Valley. I guess that makes sense. Still, you don't get how busy it is until rolling into the Badwater parking lot with at least two hundred cars parked everywhere. You can see people walking out to the low spot which is somewhere out there in valley.