I suppose this is another case where an issue is "on their radar" but any decision is a long way off. Time and time again we are seeing how slowly the wheel of progress move at The Marriott Corporation.
That said, the world is changing at breakneck speed. Businesses are merging, others are affiliating with others, even more are co-branding. All of these decisions are being made with one common goal. survival. The airlines for example, have had takeovers, mergers, and massive worldwide affiliations of their own. While the takeovers have netted a smooth transition to blend the two companies systems, mergers and 'affiliations' have proven to be a bit more challenging to completely blend the multiple companies. I suspect in Marriott's case, once the decision to merge was made, the #1 goal would have been to increase revenue by bringing the Marriott customer base into the world of AC Hotels. Smart idea, right? Only problem is that the Marriott customer base expected a seamless and immediate transition. This particular problem (gift card usage) is simply a case of Marriott under delivering on the smooth transition. An example of slow progression, I have recently been experiencing a heightened level of awareness of my elite status at Ritz Carlton. It has taken a few years to get here, but just last week I was upgraded at a Ritz. "Times-they-are-a-changin"
From the FAQs on gifts.marriott.com:
Q. Where can I use my Marriott GiftCard?
A. Marriott GiftCards can be used at any participating Marriott properties, including JW Marriott, Edition, Autograph Collection, Renaissance, Marriott Hotels and Resorts, Courtyard by Marriott, Fairfield Inn and Suites, SpringHill Suites, Residence Inn, TownePlace Suites, and Marriott Vacation Club.
Please also see Andy's response on this thread:
In my experience, hotel beds in Spain resemble billiard tables. Imagine my pleasant surprise when I stayed at the AC Hotel Ciudad Sevilla, and enjoyed nice, relatively comfortable beds! They are not quite up to par with Marriott beds, but are a vast improvement to the beds found in even expensive Spanish hotels. Additionally, the staff were terrific (and they spoke excellent English). This particular property has only one fault — ambulance sirens right on the adjacent streets, sound more or less continuously throughout the night. It must be close to a hospital, and became irritating after about 3 nights.