Multiple Parties Concurrently in the Same World?

Can you describe your experience having multiple parties in the same world?

Did it work?

Did you have what one party did have consequences on the other party? Did they hear about the exploits of the other party?

Did you run the same content for both parties? All or just some overlap?

Did they ever meet? Friendly or combative?

Did some players play in both parties? Did some characters play in both parties?

Can you provide some advice for how to do this well and what problems to watch out for?