Short Answer: With the new Healthcare.gov number just released for enrollments through 12/24, we can now estimate that ~160,000 individuals enrolled on 12/23 (!!!) (through both the state and federal exchanges), nearly twice the rate of the preceding days. That's because ~210,000 enrolled on 12/23 and 12/24 via Healthcare.gov, bringing up the total enrollment through the federal site to ~1.1 million and the nationwide enrollment to ~2 million. In the four days (12/19-12/22) leading to the big enrollment deadline (i.e., the deadline to sign-up for health insurance in time for coverage on January 1st), the enrollment rate was ~85,000/day. To put that in perspective, in October a paltry 4,200/day were enrolling. November fared only a little bit better at ~10,000/day.
If you want a more detailed explanation for why these numbers matter and how I calculated them, read below the fold.