I have wrestled with the idea of Santa Claus since my rebirth in Christ; I wondered to myself "is he an 'emissary of God'"-- which is what I want to believe with all my heart, or "is he our 'adversary'...a product of satan?" I came to the conclusion that it is possible that he can be both, depending how he is introduced.
I was very blessed to have parents who taught me from when I can first remember that Christmas was all about the 'baby Jesus'. Santa, who loved all boys and girls with all his heart, brought us joy by the gifts he gave us; he loved 'baby' Jesus' the most, and it was a celebration of his birth/day. So if I was to interject my most humble opinion, I would say that I believe Santa can't be our adversary, because he is good, a saint of Christ, and his love is representative of God's love.
As I grew up, there were two things that I longed to see at Christmas, the Christmas story re-enactment with the newborn baby in our church and his parents, and 'Santa Claus' at Bellas Hess (a dept. store we shopped at). The Christmas season was made more majical, and mystical when I would set my baby blues on Santa. My heart would drop, and my stomach would be filled with the butterflies of excitement as I stood in line waiting for my chance to sit on Santa's knee. He always so gently pulled me up on his knee, ho-ho-ho'd, then in a gentle voice would ask if I had been a good girl...of course, I wouldn't tell HIM I WAS BAD! --Always a good girl-- Then the moment--the very moment I had been waiting for--came when he would ask 'if there was anything Santa Claus could bring for me'. Boy! I think the Saint got an ear full...practically all the back pages in the Sears catalogue that advertised the 'girly toys'. Sometimes he would have to cut me off, and ask me to write a letter to him...I suppose, because there were other little boys and girls waiting to see him.
I loved the idea of Santa Claus...especially on Christmas morning when all those beautiful, some huge, packages would be crowding around the tree (4 kids)--Santa had been to OUR house! I would breathe a sigh of relief that he didn't see me that one night I played a dirty trick on my little brother, and got in trouble...or any number of other times I wasn't up to 'my shiny halo' good self. WHEW!
Even now, at the age of 46, when I see the 'Mall' Santa Claus, I get all twitter-pated--to the dismay of my children. The little kid in me just comes out, and I, excitedly, have to say hi to Santa. He always waves back to me. When I turn to rejoin my family, including my husband, they are no where to be found. "What? I had to say hi to Santa! He's only here once a year!" *giggling*
So in my humble opinion something that brings ME that much joy can't be evil, but must be born out of the love, joy, and the sharing of Jesus Christ. I am sure that some children grow up never knowing the true St. Nickolaus. The one who Santa Claus is based on. He who loved Christ so much that he gave up all his wealth to share his love and joy with others. I read that he was the youngest man to become a Bishop. I love all the folklore surrounding him, and how different regions identified this man with some sort of tradition of the jolly ol' fellar.
I had seen this in a figurine. I love it and it is on my 'page'. It is so sweet to think that the omniscent God poured into flesh should be prayed over by His precious servant, the omniscent Santa Claus.

"Santa's Prayer On Christmas Eve"
The sleigh was all packed, the reindeer were fed,
But Santa still knelt by the side of the bed.
"Dear Father," he prayed "Be with me tonight.
There's much work to do and my schedule is tight.
I must jump in my sleigh and streak through the sky,
Knowing full well that a reindeer can't fly.
I will visit each household before the first light,
I'll cover the world and all in one night.
With sleigh bells a-ringing, I'll land on each roof,
Amid the soft clatter of each little hoof.
To get in the house is the difficult part,
So I'll slide down the chimney of each child's heart.
My sack will hold toys to grant all their wishes.
The supply will be endless like the loaves and the fishes.
I will fill all the stockings and not leave a track.
I'll eat every cookie that is left for my snack.
I can do all these things Lord, only through You,
I just need your blessing, then it's easy to do.
All this is to honor the birth of the One,
That was sent to redeem us, Your most Holy Son.
So to all of my friends, least Your glory I rob,
Please Lord, remind them who gave me this job."
By Warren D. Jennings
http://jsmagic.net/xmassantasprayer/
You can find more info on the 'History of Santa Claus or St. Nickolaus at thes web sites.
http://www.stnicholascenter.org/Brix?pageID=35
http://www.thehollandring.com/truestory.shtml
http://www.the-north-pole.com/history/
http://www.claus.com/village.php