If you type a sequence of letters too quickly ("mi"), the dropdown narrows to a single item and the textbox is completed with the first item in the list that matches that criteria ("Michigan"). Do you think there might be a way to get around that?

This textbox isn't designed for "industrial strength," so issues like this will occur. If you want to try to fix it, you'd need to use a timeout such as:

    this.textbox.onkeyup = function (oEvent) {

        //check for the proper location of the event object
        if (!oEvent) {
            oEvent = window.event;
        }

        //call the handleKeyUp() method with the event object

        clearTimeout(this.timeoutID);
        this.timeoutID = window.setTimeout(function () { oThis.handleKeyUp(oEvent);},250);

    };

Nicholas C. Zakas
Author, Professional JavaScript for Web Developers (ISBN 0764579088)
http://www.nczonline.net/

How can I return focus to the textbox after the Enter key is pressed?

I tried the code modification the author posted above, but it disabled the typehead and dropdown - although you could still type in the textbox, and no js error was produced, at least in Firefox.

Has anyone had success with this modification? If so, I'd appreciate knowing exactly what you did. Thanks.