I have to side with the customer in this case. You booked and paid in full for a rate that included certain amenities. For the hotel to send an e-mail the day before check-in basically saying, "Sorry, we made a mistake and you're not going to get what you thought you already paid for," really rubs me the wrong way.

A well-run hotel would have quietly corrected the error for future bookings, but honored the ones that were already made. At the absolute bare minimum least they could do, they should have sent a much more elegant apology note asking if some degree of compensation (points, free drink vouchers, SOMETHING) would be acceptable as a token of their apology.