Last month we replaced our old 2003 domain controllers with 2008 domain controllers. The process went smoothly.
Preped domain for 2008,
DCPromo'd new DC's
Moved FSMO Roles and time server.
Demoted old DC's
And ran clean DCDAIG's during and after procedure.
Now everything is working fine except when you view the network, only LAN computers show up.
Previously, all domain computers were shown when you browse the network.
We have several remote offices connected by VPN's.
Those remote computers all log in normally, and are available from the LAN via \\computername.... but no longer show up when you browse the network.
All computers are windows 7
Thus, you need WINS. WINS was enabled by default with 2003 but is not with 2008 or newer. You need a WINS server at each site.