It's been a while since I've done any large-scale AD administration so I'm reaching back a bit here. I remember that there are certain security related attributes on a user account object that, due to their nature, are flagged for immediate propagation to other sites.
I have a case where passwords resets are not being propagated until scheduled replication happens. I had thought that was a case of immediate propagation. Am I just remembering incorrectly?
Domain function level is 2003.
Yep, you are, passwords are propagated on the normal schedule. I'll connect to a DC in the site closest to the user when I need it to take immediate effect or when I forget I'll jump into Sites and Services and force a replication to the site the user is in.
Look at the urgent replication section here:
http://technet.microsoft.com/en-us/library/cc772726(WS.10).aspx#w2k3tr_repup_how_huzs