When installing, one of the steps is adding a user in firstboot. Not having this user show up in the list of the greeter seems suboptimal
Totally agree. GDM gets the list of users from ConsoleKit. See ck-history --frequent. I guess firstboot should tell ConsoleKit about the new user. Jon, what's the best way to do that?
It's more than just firstboot, though. It's just as true if I add a user via system-config-users. Or useradd in the livecd initscript. While ck-history --frequent could be nice for the case where I have centralized account management and not wanting to deal with lag to get account lists via nis or AD, in many deployments (especially with Fedora) that's just not the case. Instead it's a small number of local accounts. So I really think this is better fixed in gdm than having to spread changes all over the world.
Jon made GDM include local users now.