One additional note, when I look at the "POST usergroup.asmx" Response (Net tab) in IE's Dev Tool, it shows the following:
<?xml version="1.0" encoding="utf-8"?><soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema"><soap:Body><GetUserInfoResponse xmlns="http://schemas.microsoft.com/sharepoint/soap/directory/"><GetUserInfoResult><GetUserInfo><User ID="16" Sid="S-1-5-21-1383155457-1796633636-1831341646-22317" Name="MY NAME" LoginName="MYDOMAIN\My.NAME" Email="MY.NAME@DOMAIN" Notes="" IsSiteAdmin="False" IsDomainGroup="False" Flags="0" /></GetUserInfo></GetUserInfoResult></GetUserInfoResponse></soap:Body></soap:Envelope>