here's what I currently have, unfortunately I cannot seem to figure out how to get autoFill to work with jQuery-UI... It used to work with the straight up Autocomplete.js

<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.4.2/jquery.min.js" type="text/javascript"></script>
<script src="http://ajax.googleapis.com/ajax/libs/jqueryui/1.8.1/jquery-ui.min.js" type="text/javascript"></script>
<script src="http://jquery-ui.googlecode.com/svn/tags/latest/external/jquery.bgiframe-2.1.1.js" type="text/javascript"></script>
<script src="http://ajax.googleapis.com/ajax/libs/jqueryui/1.8.1/i18n/jquery-ui-i18n.min.js" type="text/javascript"></script>

<script language="javascript" type="text/javascript">


    var thesource = "RegionsAutoComplete.axd?PID=3"
    $(function () {
        function log(message) {
            $("<div/>").text(message).prependTo("#log");
            $("#log").attr("scrollTop", 0);
        }

        $.expr[':'].textEquals = function (a, i, m) {
            return $(a).text().match("^" + m[3] + "$");
        };

        $("#birds").autocomplete({
            source: thesource,
            change: function (event, ui) {
                //if the value of the textbox does not match a suggestion, clear its value
                if ($(".ui-autocomplete li:textEquals('" + $(this).val() + "')").size() == 0) {
                    $(this).val('');
                }
                else {
                    log(ui.item ? ("Selected: " + ui.item.value + " aka " + ui.item.id) : "Nothing selected, input was " + this.value);
                }
            }
        }).live('keydown', function (e) {
            var keyCode = e.keyCode || e.which;
            //if TAB or RETURN is pressed and the text in the textbox does not match a suggestion, set the value of the textbox to the text of the first suggestion
            if ((keyCode == 9 || keyCode == 13) && ($(".ui-autocomplete li:textEquals('" + $(this).val() + "')").size() == 0)) {
                $(this).val($(".ui-autocomplete li:visible:first").text());
            }
        });
    });


</script>

I've used the answer here to get the mustMatch working, but unfortunately if I "tab" away from the input box, I get the "Nothing selected" response instead of an Value and ID.

Does anyone know how to extract the ID out of the autocomplete when you don't actually select the field?