Just to be sure I've got this right.... with the mandatory profiles, they're basically shared computers that have a common login correct? Are all your users going to be domain users in one form or the other? I.E you're not allow joe schmoe who comes across your site to register on it and get an account. If that's the case then I think I may have a solution for you that might work. It won't have the automatic login but it'll solve the confusion when manually logging in.

Oh, and for clarification the web page is viewable from the public (all outside machines), a public computer lab (within our network w/ a common login), and then a staff intranet section, which is basically nothing more than a tab that shows up when authorized users are signed in.  (A mix of common logins and a few individuals.) 

I just need to simplyfy this for the users- eliminating the choice between standard and Windows logins, not requiring the domain as part of the username, etc.  Looking at the AD Guide again, I think the "intranet/Extranet Site" setup would work (no IIS prompts every time someone visits the site) but iirc when using the WindowsSignin link I couldn't get that nifty little script that plugged the the domain in before the username working.

Intranet/Extranet would be the ideal solution. The only holdback to me would be the common sign-on but if that's not a real issue on your end then, yes, it's the way to go.

I'd have to look into whether IIS can specify what domain a user logs in from. I've never noticed that before. If you can find it please let us know.