Wikipedia, that font of all current knowledge, describes "Minnesota Nice" as "courteous, reserved, and mild mannered".  If everyone in the world disciplined themselves to be like that, the world would be a better place.  If everyone in your new organization were that way, your onboarding would be that much easier.

Be Do Say

The trouble starts when people pretend to be nice, but they're not.  They might say all the right things.  They might even do all the right things.  But if being courteous, reserved and mild-mannered is not what they truly believe is right, they can't keep it up for ever. They might try.  They might say yes to what you ask them to do, thinking and hoping they will actually do it.  They might not know they're being passive aggressive.  But they are.

It's a trap

Don't get me wrong.  It's nice to be nice.  I hope everyone you meet in your new organization is truly nice.  You should hope so to.  Just be ready for the possibility that not everyone is actually as nice as they initially portray themselves.

Got any good examples?