One of the things that can be done if you run a dhcp service and a dns service is that you can dynamically update the dns (named) for your hostname with the ip address assigned by dhcpd. If you run dnsmasq, it will also dynamically update its dns with your hostname for the ip address supplied by dnsmasq's dhcp service.
On the client system (the one asking for dhcp to assign an ip address), this is supported by DHCP_HOSTNAME=<whatever> in the /etc/sysconfig/network-scripts/ifcfg-xxxx file for a system connection. For a user connection, the variable is "dhcp-hostname" in the xml file of ~/.gconf/system/networking/connections/.../ipv4/
If the appropriate variable is set, then dynamic dns works and you hostname is entered into the dns database. This all workls today with NetworkManager.
Sometime prior to Fedora 11, a /etc/dhclient-ethX.conf file was needed to fake things and get the hostname passed to the dhcpd server. This is no longer needed in Fedora 11 and, in Fedora 12, system-config-network no longer creates this file.
Unfortunately, in order to set these variables for the hostname, you currently need to use you favorite text editor such as vi. In the case of a system connection (a connection available to all users), you can use system-config-network to set the hostname value for dhcp. If a system connection is converted to a user connection, then the hostname is properly defined.
Again, everything works. BUT, I consider it to be unreasonable to set the hostname via to process described above. I should be able to set the value in NM's connection-editor ... but I currently cannot do this. I consider this a bug but (I believe others such as the developers) will consider it an RFE (enhancement).
It is wishful thinking to get this into F12. Whatever my BZ report will be, it will be against rawhide with the expectation that it be done in F13 with (hopefully) backporting to F12 and F11.
While doing a few lines of C code such as I did for DEFROUTE is not difficult, I am illiterate as far a glade is concerned and the connection-editor uses glade for its gui. I am more likely to screw things up than fix things with respect to glade ... I have no idea of where to begin as far as glade goes.