My friend, Scott Holman, gives a good warning for us to not overshadow and marginalize the incarnation by running too quickly to the Cross:
My gut tells me that some would rather pass over the baby at Bethlehem for the glories of the cross. It's easier to preach and easier to explain through propositional arguments. Generally, one would rather stand meditating on the sight of the cross than meditating on God as a baby in a feed trough.
But there is something about God coming to us as a vulnerable, needy baby that reformed people especially need to think on. The God of glory needs us to change his diapers. He is as inviting and approachable as any baby we encounter. What do we do with that?