Changing a Collection While Enumerating in .Net 4.0

We've probably all done it at one point, tried to remove an item from a collection in the middle of a ForEach enumeration and gotten an exception for our trouble -- you can't change a collection in the middle of enumerating it. The Coordinated Data Structures coming in .Net 4.0 change that, giving us threadsafe collections for parallel programming that allow changes while enumerating.