Here is what I gather, jci.
You may file a reply brief in response to the appellee's answering brief, but it is not required. Your reply brief is due 21 days after the
service of the answering brief, and is limited to 10 pages. So, I too am coming up with the December 3 due date - however I would definitely check with the Court on this, as you do not want to file late. The 25th date is when all answers must be filed by the appellee. Again, check with the Court to verify, and it is always recommended to get the filing done early if possible, as any late filing is not considered.
In your reply brief, you cannot raise any new issue or argument, nor should it be a repeat of your original opening brief (although small snippets of your opening brief may be used for clarification purposes).
The purpose of your response, should you even need to file one, is to respond to any points raised by the appellee's answering brief that you did not address in your opening brief. If you addressed all points in your opening brief, you should not file a response brief.
In addition, you may respond to all answering briefs, should you have more than one filed in response to your original brief. Again, however, you only need to file a response if new points are raised that you did not already address in your opening brief.
If you check out "Michigan Supreme Court appellee reply briefs" and "Michigan Supreme Court appellant reply briefs" online, you can see some of the forms these briefs take. All follow the court rules, but there are variations that are acceptable. I made a note of a couple for you to check - and then totally lost the examples in my mountain of papers here. If I ever locate them, I will post back.
Edit to add: A "nice looking" appellant reply brief can be found at
http://courts.michigan.gov/supremecourt/clerk/11-07/131654/131654-index.htm.