jQuery is very slow at handling poor browsers, this script added a 7.8x perf improvement

FastJQueryForIE7

/*
 * Faster jQuery DOM traversal for <= IE7. 
 * Usage: 
 *  $Q() is a drop-in replacement for $(). Returns same jQuery object.
 * 
 *  //$Q = $; //Un-comment, to switch to use jQuery for benchmark comparisons
 *  My avg benchmarks in IE7 for traversing a 20x30 table was: 
 *  786ms vs 6140.67ms - Chrome can do it natively in 28ms
 *
 * Limitations:
 *   Requires an Id (i.e. #) or Tag Name (e.g. INPUT) in each child selector.
 *   Requires jQuery and returns a $()
 * 
 * Valid Examples:
 *   - TBODY TD.c1 INPUT
 *   - TH.c1 STRONG
 *   - #btnSubmit SPAN
 *   - TBODY INPUT[name='chkProcess']
 *   - TBODY INPUT[type='text']
*/

//NOTE: first-draft, adds vars to global namespace: doc, $id, $tag, $el, $find, $Q

var doc = document, $id = function(id) { return doc.getElementById(id); }, 
    $tag = function(tag) { return doc.getElementsByTagName(tag); }

function $el(sel)
{
    if (typeof sel == 'string')
    {
        return sel.charAt(0) == '#' 
            ? $id(sel.substring(1)) 
            : $tag(sel)[0];
    }            
    return sel;
}

function $find(rootEl, tagSel)
{
    var parts = tagSel.split('.'), tag = parts[0], cls = parts.length == 2 && parts[1];            
    var el  = $el(rootEl);
    var filterPos = tag.indexOf('['), filterName, filterValue;
    if (filterPos != -1) {
        parts = tag.substring(filterPos + 1, tag.length - 1).split('=');
        filterName = parts[0], filterValue = parts.length == 2 && parts[1];
        if (filterValue && filterValue.charAt(0) == "'") {
            filterValue = filterValue.substring(1,filterValue.length-1);
        }
        tag = tag.substring(0,filterPos);
    }
    var els = el.getElementsByTagName(tag);
    if (!cls && !filterName) return els;
    var results = [];
    for (var i=0,len=els.length; i<len; i++) {
        var childEl = els[i];
        if ((!cls || (childEl.className && childEl.className.indexOf(cls) != -1)) 
            && (!filterName || childEl[filterName] == filterValue)) 
        {
            results.push(childEl);
        }
        
    }
    return results;
}
        
function $Q(selector) {            
    if (document.querySelectorAll) return $(selector); //shortcut to native eval in jQuery for decent browsers
    var els = [], resultSet = [[document]];
    var args = selector.split(' ');
    for (var i=0,len=args.length;i<len;i++) {
        var parentSet = resultSet[i];
        if (parentSet.length == 0) return $([]); //short-circuit

        var sel = args[i], results = [];
        if (sel.charAt(0) === '#') {
            resultSet.push([document.getElementById(sel.substring(1))]);
            continue;
        }
        for (var j=0,jlen=parentSet.length;j<jlen; j++) {
            var els = $find(parentSet[j], sel);
            for (var k=0,klen=els.length; k<klen; k++) {
                results.push(els[k]);
            }
        }
        resultSet.push(results);
    }
    
    return resultSet.length > 1 ? $(resultSet.pop()) : $([]);
};