title: Observable.FromAsync what is IScheduler argument for?
body: <p>I was trying to execute that Reactive + ReactiveUI Code</p>
  <p><code>Observable.FromAsync(async () =&gt; //async code that must run on UI Thread, RxApp.MainThreadScheduler);</code></p>
  <p>But that doesn't get executed on MainUIThread.
  Can anyone tell me what's the point of having IScheduler as parameter since it doesn't seem to get executed on UI?</p>