Distance between two Latitude/Longitude points

So when I asked my friend Kerry (who BTW is the king when it comes to map projections) how to calculate the distance between two lat/lon points ? he pointed me to this link. He followed by saying "This is a good start, but what I have implemented in Java, takes care of all the 'weird' conditions!". This is why he is the king :-). So you can find the AS3 implementation here. And here is a simple MXML calculator.

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="absolute">
  <mx:Script>
    <![CDATA[
      import com.esri.aws.awx.utils.Utils;
      private function onClick() : void
      {
        var lat1n : Number = Utils.parseDeg(lat1.text);
        var lon1n : Number = Utils.parseDeg(lon1.text);

        var lat2n : Number = Utils.parseDeg(lat2.text);
        var lon2n : Number = Utils.parseDeg(lon2.text);
       
        var dist : Number = Utils.distVincenty( lat1n, lon1n, lat2n, lon2n);
        distLabel.text = dist.toFixed(2) + " meter(s)"
      }
    ]]>
  </mx:Script>
  <mx:Form width="100%" height="100%">
    <mx:FormHeading label="Geodesic Distance Calculator"/>
    <mx:FormItem label="lat 1:">
      <mx:TextInput id="lat1" width="200" text="53 09 02N"/>
    </mx:FormItem>
    <mx:FormItem label="lon 1:">
      <mx:TextInput id="lon1" width="200" text="001 50 40W"/>
    </mx:FormItem>
    <mx:FormItem label="lat 2:">
      <mx:TextInput id="lat2" width="200" text="52 12 19N"/>
    </mx:FormItem>
    <mx:FormItem label="lon 2:">
      <mx:TextInput id="lon2" width="200" text="000 08 33W"/>
    </mx:FormItem>
    <mx:FormItem label="dist">
      <mx:Label id="distLabel"/>
    </mx:FormItem>
    <mx:FormItem>
      <mx:Button
        label="Calculate"
        click="onClick()"/>
    </mx:FormItem>   
  </mx:Form>
</mx:Application>