I now have the new AD authentication module up and running on a bunch of different portals, and in use by hundreds of people... It works great!
There are a few quirks though that I have yet to be able to resolve...
I have most of the people logging in using a button I put on the page that redirects them to the WindowsSignIn.aspx file. That works great from inside of the district, and from outside of the district they now get a login box where they can type in their name using two different formats (DOMAIN\Username or Username@DOMAIN.COM).
The issues I'm running into right now:
1. No matter what I enter into the "Auto-login IP Address" field, I cannot get users "automatically" authenticated simply by visiting the website from the local Intranet.
2. When I click the link to log into the website using the WindowsSignIn.aspx file, all works well, I'm logged in with Admin privileges. When I log in, using the same account, using the standard login box, I'm authenticated but I'm not part of the admin group anymore.