Iterating through each grid row and matching elements to largest height
Can't say if this is much faster, but it's more concise

jQuery(document).ready(function($) {
    "use strict";

    var firstItems = $('.item.first');

    firstItems.each(function() {
        var $first, row, headings, heights, maxHeight;

        $first = $(this);

        // Get collection of "columns"
        row = $first.add($first.nextUntil(firstItems));

        // Find each column's heading
        headings = row.find("h2"); 

        // Get the heights of the headings
        heights  = headings.map(function () {
            return $(this).outerHeight();
        }).toArray();

        // Get the maximum
        maxHeight = Math.max.apply(null, heights);

        // Set the heading heights to the maximum
        headings.css("height", maxHeight);
    });
});​​​


--Edit--

In my particular instance, the above script had conflict issues with prototype, since it lives inside a Magento install. I sought help and found this improvement.

/Jezen