RobertTheTraveler - Am posting right now from a Residence Inn on an Entertainment rate booked with code NPR.
I have stayed in the past two months at properties in Texas, Alabama and Massachusetts on weekend Entertainment/NPR rates.
Availability seems to vary widely among markets and occupancy levels, but checking for the one or two properties that may have the "50 Percent" weekend Entertainment rate can be worthwhile, if random. (The default 10 percent off usually is higher than other available rates).
Incidentally, this stay is the first time I've been asked to show the card at check-in.