Mango relocks the device on update, which prevents users from ChevronWP7 unlocking up through build 7661. In the users' case, this basically means, if you don't have a legitimately unlocked device, you won't be able to stay unlocked on Mango. Fortunately, XDA Developers member yhd4711499 has figured out a method to unlock your Samsung Omnia 7 once you've updated to Mango. Samsung Focus devices seem to have limited success, but it may be worth a shot.

The method requires you to have NoDo unlocked, and you must copy a provisioning XML over where the built-in diagnostics app can read it, which will then jailbreak Mango. Interested? Head on over to XDA Developers for the instructions.