Reactive Extensions in .NET – Observable Collections

Last week I was reading about the two new interfaces introduced in .NET Framework 4.0 – IObservable & IObserver.In first place they seemed to be just simple interfaces providing a mechanism to implement the Observer (GoF) design pattern.But soon I found out that really meaningful implementations of these are actually present in the Reactive Extensions for .NET.This is a separate class library released as a MSDN DevLabs project and not part of .NET Framework till now.