title: What are the similarities / differences between Control.Observable and Control.Event modules in F#?
body: <p>F# (at least in Visual Studio 2012) has both <a href="http://msdn.microsoft.com/en-us/library/ee370313(v=vs.110).aspx" rel="noreferrer"><code>Control.Observable</code></a> and <a href="http://msdn.microsoft.com/en-us/library/ee340422(v=vs.110).aspx" rel="noreferrer"><code>Control.Event</code></a>.</p>
  
  <ul>
  <li>How are they related?</li>
  <li>Which one should be used when?</li>
  <li>Are there performance differences between the two?</li>
  </ul>
  
  <hr>
  
  <p>I would also love to know what Haskell modules / packages / features the .NET <code>IEnumerable</code> / <code>IObservable</code> duality achieved with <em>reactive extensions to .NET</em> correspond to.</p>