Same issue - some are still waiting from December 15th. Was looking to post about this but will just add my complaint to your post. Hope someone from support notices.
Hi, I am the gifter of the game One By One which you won.
Steam Community :: Delisper is a link to my profile page. You should be able to add me on steam and I can message you the key.
Just checked my "stuck giveaway" and it is now on the giveaway in progress list. This time I do not need to contact support. Hopefully the others in this situation will have their issues resolved too :).
Edit: no, got mixed up, my game was still stuck. Sent off an email to support and they...