DEFINITELY apply early. Apply as soon as you can. Apply sooner!
When I was going through the process, I was told by the pre-med adviser and by other folks who had applied in previous years (not on SDN - didn't discover this until it was pretty much too late) that applying early gives a SLIGHT advantage. I didn't turn my AMCAS application in until October, counting on pretty good numbers to catch some eyes at the schools I applied to. Didn't work! Out of 11 completed applications, I got 4 interviews, 2 of which were in April and were only for "wait-list" spots. One of the 4 rejected, 2 have put me on a wait list, and the fourth hasn't responded yet. I fear having to apply again, because I missed the "slight" advantage of applying early.
Learn from my mistake, PLEASE! I've had a little flavor of hell as I've endured not having any idea where my life is going in the next year.
On the other hand, a classmate of mine whose qualifications were similar applied two or three months before I did and got 4 acceptances in addition to wait list spots. Applying early makes a difference and can be a KEY to success in this grueling process.
Good Luck.
P.S. Thanks for enduring the length of my post!