Default report is available in report -> sales -> coupans.
And with script you can find used coupan count and customer details very easily :
$coupon = Mage::getModel('salesrule/coupon/usage'); $coupon->load('coupan_id', 'code'); if($coupon->getId()) { $timesUsed = $coupon->getTimesUsed(); $customer = $coupon->getCustomerId(); echo $timesUsed; echo $customer; }