Just finished performed Inter-forest migration from Win2k3 to Win2k8 domain controller.
On this Migration, i have achieved:-
a) Group account migration
b) User account and password migration
c) Computer account migration.
Most of the time, i've performed a lot of configuration on the source dc and target dc.Just a little interaction on the the workstation.
Now all XP and Vista workstation has successful migrated to new domain without a lot of interaction. (everything is automated from target dc)
It is not an easy and straight forward tasks. You need to do some troubleshooting in order to successfully perform inter-forest migration.
If you want to perform this tasks, my advise is perform the migration after office hour. Some issue you need to consideration in order to make it successful...