Most pre-dents are going to be telling you - YES - your application is late, blah, blah, blah. I know both times I applied to d-school, I submitted my application 'late' according to SDN standards - Aug in 1995 and mid-Sept in 2005. Both times, I still had all my interviews by mid-Nov and received all my acceptances on the Dec 1st selection. As long as you have competative stats, you will most likely get interviews before the cut-off for the Dec1st selections.
What you need to realize is that SDN is filled with type A gunners. So, if you didn't submit your application within the first month, you are late in their eyes. Relax, you will be fine.