title: What's the difference between SubscribeOn and ObserveOn
body: <p>I just discovered <code>SubscribeOn</code>, which makes me wonder if I should be using that instead of <code>ObserveOn</code>. Google took me <a href="http://social.msdn.microsoft.com/Forums/en-US/rx/thread/6944f097-00f4-42ad-8f19-d01d1aa939f4/" rel="noreferrer">here</a> and <a href="http://www.jaylee.org/post/2011/07/24/Rx-Using-the-ObserveOn-and-SubscribeOn-operators.aspx" rel="noreferrer">here</a>, but neither have helped me grok the difference: it seems incredibly subtle.</p>
  
  <p><em>(In my context, I've got events 'coming up' on a non-gui thread, and I need to switch over to a gui thread before using the event data to update controls).</em></p>