Will be in the Bay area in early to mid December, and have never been to Muir Woods despite visiting San Francisco and environs many times over the years. At this time of year is it worth the drive to see the Redwoods, or should I save this for another visit?

If the weather is clear, go. It should be quite lush.

Winter is my favorite time in the redwoods. If it has been raining, it will be damp and fragrant. And of course, pretty lush. Rains wash away the dust and pollin, so all the plants are very clean. There aren't a lot of deciduous plants in a redwood forest, so just about everything should have its leaves.

Even if the day is stormy, if it isn't really windy and you don't mind taking a walk in the rain, I would go.