A point for Insiders intending to stay in one or more of the AC Hotel range in Spain to note:
The process of embedding these hotels into the Marriott portfolio is in its "transition" phase. I stayed at two - in Madrid and Valencia - last month; the only point of difficulty arose in deciding whether the tariff I used - the Senior rate - qualifies for the "nights stayed total" and MR points. Both hotels were initially inclined to think that this rate did not qualify. It took a couple of calls to MR to clarify that the Senior rate did qualify.
If any of you are likely to be in the same situation, it might be worth checking before/when you leave that the Hotel recognizes your rate as qualifying for MR benefits etc.
Apart from this, I found each hotel to offer a very acceptable level of service within the terms of the facilities they offer.