You are right it is quite labour intensive at first. Especially if trying to adapt it to an existing campaign world. If your building your own and doing it from the beginning however it can be quite rewarding. Would want to try and push it on Forgotten Realms fx though. That would almost be a...
I realize I may be late to the party but only just registered and just thought I'd give another option as well.
Eden Studios has released a book called fields of blood-book of war, which in IMO gives a good alternative to realms management.