IObservable and IObserver will now be very convenient for something I'm working on.
Is there a similar set of interfaces and classes for .NET 3.5?
Or should I wait for .NET 4.0 before I can use them?
This blog post - Rebasing System.Reactive for the .NET CLR - explains how you can get .dlls from the Silverlight Toolkit to work with .NET 3.5. Do not miss the update at the end (and comments).
I did re basing and created a small WPF drawing application. Here is the source code
LINQ to Events - More About .NET Reactive Extensions (Rx) and .NET 3.5 WPF Demo