Here's what I've done so far:
1) I created a Site Column at the home site level.
2) I went to the document library in question, and added the column from existing site columns, making sure to say "add to all content types".
3) I published my InfoPath form(s) (as Administrator-approved templates, just in case it matters). In the publish wizard, I specified the new field to be promoted, making sure to map it to the correct group and column from the sharepoint site.
4) I added the column to a view so I could see it in the library.
5) I didn't see it.
I even tried creating/saving some documents, thinking that maybe that would refresh/recopy the field. It didn't.
At one point I even went back to the site level, opened up my content types, and hand-added the column to each one, since it didn't show up there. No luck.
Does anyone have a clue here? I'm pretty new to this Sharepoint/Infopath world, and it seems like it could do a whole lot... if it would actually work.
Thanks!