Ah, figured why only that one site was back to pre-December traffic ... it promptly surpassed it. The site normally gets 3000 impressions a day, yesterday it got 5000. Hopefully this bodes well for the rest of the year My other sites are all on a gentle post-holiday rise, this one had a very steep rise.
Maybe because people going on holidays, I am sure your traffic will be back to normal ater 1-2 weeks after new year