Had a fantastic 1 night stay at the St Regis on the Corniche Abu Dhabi.
Booked the base 1 king bed room through Amex FHR, upgraded to the St Regis suite on arrival (I also hold Marriott Gold status fwiw). 100$ credit to be spent at the property, free breakfast (fantastic selection, from 10 types of croissants to a dedicated "health" section) and 4 PM late checkout (which was extended further to 5 PM). Great facilities, friendly staff and an enjoyable beach club. All in all would recommend staying here.