Will Ubuntu 11.04 use Gnome 3? If so, what differences for end-user is going to be? I know that there won't be Gnome shell, but what about the login screen? Will Ubuntu continue using that old (GNOME 2.X) one, or create its own, or use the new Gnome 3 login screen (maybe it will be a part of gnome shell? http://live.gnome.org/GnomeShell/Design/Whiteboards/LoginScreen)?
Original answer (now incorrect):
dv3500ea's answer was the original goal however this didn't end up happening. Sebastian Bacher posted an update to the ubuntu-desktop mailing list in January.
and later on:
Right now Nautilus, and the other components of the GNOME desktop are 2.32.
However you can try GNOME 3 via PPA by following the instructions in this answer: