I'm using the following method to resolve UrlPicker values to a POCO:

/// <summary>
/// Resolves the value of a UrlPicker datatype to a .NET object
/// </summary>
/// <param name="urlPickerXml">The value of the UrlPicker in XML format</param>
/// <returns>A UrlPicker .NET object</returns>
public static UrlPicker ResolveUrlPicker(string urlPickerXml)
{
    XmlDocument xmlDoc = new XmlDocument();
    xmlDoc.LoadXml(urlPickerXml);

    UrlPicker urlPicker = new UrlPicker()
    {
        Mode = (UrlPicker.UrlPickerMode)Enum.Parse(typeof(UrlPicker.UrlPickerMode), xmlDoc.SelectSingleNode("//url-picker").Attributes["mode"].InnerText),
        Url = xmlDoc.SelectSingleNode("//url").InnerText,
        NewWindow = bool.Parse(xmlDoc.SelectSingleNode("//new-window").InnerText),
    };
    XmlNode linkTitleElement = xmlDoc.SelectSingleNode("//link-title");
    if(linkTitleElement != null)
        urlPicker.LinkTitle = linkTitleElement.InnerText;
    if (!string.IsNullOrEmpty(xmlDoc.SelectSingleNode("//node-id").InnerText))
    {
        urlPicker.NodeId = int.Parse(xmlDoc.SelectSingleNode("//node-id").InnerText);
        urlPicker.Url = umbraco.library.NiceUrl(urlPicker.NodeId.Value);
    }

    return urlPicker;
}

And this is the POCO class:

/// <summary>
/// POCO for UrlPicker
/// </summary>
public class UrlPicker
{
    /// <summary>
    ///  The mode (url/content/media/upload)
    /// </summary>
    public UrlPickerMode Mode { get; set; }
    /// <summary>
    /// The url
    /// </summary>
    public string Url { get; set; }
    /// <summary>
    /// Open in new window?
    /// </summary>
    public bool NewWindow { get; set; }
    /// <summary>
    /// The link title
    /// </summary>
    public string LinkTitle { get; set; }
    /// <summary>
    /// The node id
    /// </summary>
    public int? NodeId { get; set; }

    /// <summary>
    /// Enum for UrlPicker modes
    /// </summary>
    public enum UrlPickerMode { URL, Content, Media, Upload }
}