<?php

class Company_Bestseller_Block_Bestseller extends Mage_Catalog_Block_Product_Abstract
{
    public function getBestsellerProducts()
    {
        $storeId = (int) Mage::app()->getStore()->getId();

        $date = new Zend_Date();
        $toDate = $date->setDay(1)->getDate()->get('Y-MM-dd');
        $fromDate = $date->subMonth(1)->getDate()->get('Y-MM-dd');

        $collection = Mage::getResourceModel('catalog/product_collection')
            ->addAttributeToSelect(Mage::getSingleton('catalog/config')->getProductAttributes())
            ->addStoreFilter()
            ->addPriceData()
            ->addTaxPercents()
            ->addUrlRewrite()
            ->setPageSize(5);

        $collection->getSelect()
            ->joinLeft(
                array('aggregation' => $collection->getResource()->getTable('sales/bestsellers_aggregated_monthly')),
                "e.entity_id = aggregation.product_id AND aggregation.store_id={$storeId} AND aggregation.period BETWEEN '{$fromDate}' AND '{$toDate}'",
                array('SUM(aggregation.qty_ordered) AS sold_quantity')
            )
            ->group('e.entity_id')
            ->order(array('sold_quantity DESC', 'e.created_at'));

        Mage::getSingleton('catalog/product_status')->addVisibleFilterToCollection($collection);
        Mage::getSingleton('catalog/product_visibility')->addVisibleInCatalogFilterToCollection($collection);

        return $collection;
    }
}

<?php foreach ($this->getBestsellerProducts() as $_product): ?>
    <?php if($_product->getRatingSummary()): ?>
        <?php echo $this->getReviewsSummaryHtml($_product, 'short') ?>
    <?php endif; ?>
<?php endif; ?>

Mage::getModel('review/review')->appendSummary($collection);