I'm running a site for a K-12 environment, although it is nowhere near as good-looking as yours...  Did you hire someone to make a custom skin?

I've been running it since v3.0, so it's undergone a LOT of upgrades.  In fact, it has had so much done to it that it now it has more hourly exception errors than I can fix.  I cannot even upgrage it anymore!  At this point, a nuke-and-pave approach looks like our best bet.  So, next week we're putting a whole new website online, a fresh install.  I'd give you a link to it, but right now I'm embarassed to show it, and next week it will look totally different anyways... *grin*

Version 4.6.x introduced a whole new design to the AD integration, and I haven't really gotten a chance to test it out yet.  I'll find out next week how much we'll have to change to get it usable here.  Right now, it is in mixed-mode, and the only way the AD users get automatically logged on is to visit the WindowsSignIn.aspx URL.  I pushed this URL out via GPO to everyone's favorites, and forced it as the start-up page for the students in IE.  On the login page (I had made a custom one, but now that one is gone), I put a button for domain users to click on to log in, right above the "public" login.