I am successfully using a .NET (4.0) extension for accessing the Google Maps API. However, it is slooooow - like ~3 sec for the screen to update with the resulting mileage. Here is my (pseudo-)code in the dll:

using System;
using System.IO;
using System.Net;
using System.Xml;

byte[] response;
string url = "https://maps.googleapis.com/maps/api/distancematrix/xml?sensor=false&units=imperial&origins=<MyOrigin>&destinations=<MyDestination>";

using (WebClient wc = new WebClient())
{
    response = wc.DownloadData(url);
}

MemoryStream ms = new MemoryStream(response);
XmlReader reader = XmlReader.Create(ms);

reader.ReadToFollowing("distance");
reader.ReadToFollowing("value");
string strMeters = reader.ReadInnerXml();
int intMeters;
Int32.TryParse(strMeters, out intMeters);
return intMeters / 1609;

Nothing too fancy. I would think that doing this repeatedly would speed things up, so that the code is cached, but that doesn't help. Any suggestions on how to improve the response time?