I got a December letter last year and received it on Dec 13th. I think they send them a few days early so you won't be calling asking where your letter is. FYI calling to ask if you made it is frowned upon.
Congrats to you guys that got accepted. One thing I did last year was make a facebook group for our class and we got about 1/3 of the class to join before orientation even started.
ALSO!! The pre-matriculation program is great. If you got an early letter you might not have gotten the flier for it. It's a great chance to find your way around campus, find out a thing or two about how things work, take a practice computer exam, get some free lunches, hear presentations from different specialties on what it's like, get some practice lectures from M2's (dull but I picked up a few good things), and most of all make some of the best friends you'll have through out med school.
If you have questions PM me.