I'm not a Christian so I'm probably not the best person to answer this question, but here's my opinion.
I see Christmas as a time for families to come together. Some families only get together at this one time of year, and bonds are strengthened through the expressions of love and giving of gifts. This may have nothing to do with the Christian idea of celebrating Christ's birth, but if you do believe in Christ, what better day to celebrate family than on his birthday?
I see no harm in the Santa myth. It's no more harmful to children than the Easter bunny or Tooth Fairy, and these fun experiences are chances for children to develop fond memories with their family that they will take with them throughout their life. Of course there are everyday opportunities to cherish and treat our children in special ways, but with today's busy lifestyles we forget to make time for special moments. Annual holidays act as reminders to make time for special moments.