some information about my experience for anyone interested.
the pre-paid amex cards are in $25 increments so for the $150 I received, i got six cards.
even though my room was pre-paid, the hotel took the cards and applied them to my folio which resulted in a reimbursement of the $150 which was much easier than trying to spend six low value cards.
overall, this was a very good deal which resulted in two nights at $85. Had I been willing to change hotels, I would have gotten the first night at about $60 since the rebate is $100 the first night and $50 the second.
the going rate was around $170 the nights i stayed when i looked about a week out.
overall, a very good experience.