Just to confirm that this bug hits openSUSE 12.2 as well, as it affects gdm 3.4 in any distro. I got it on ArchLinux since Gnome 3.4 and found this bug report about Fedora: GDM no longer ignores user accounts unless shell denies login.

Code:
# rpm -q gdm
gdm-3.4.1-4.5.1.x86_64

tengel 2012-06-20 19:59:33 EDT

Confirmed here as well - with mine it's the NX (No Machine) user that can't have the shell changed, so I'm stuck with it's account in GDM.

# cat /etc/passwd | grep ^nx
nx:x:992:988::/usr/NX/home/nx:/usr/NX/bin/nxserver

# cat /etc/login.defs | egrep "(G|U)ID_MIN"
UID_MIN 1000
SYS_UID_MIN 201
GID_MIN 1000
SYS_GID_MIN 201

# rpm -q gdm
gdm-3.4.1-3.fc17.x86_64