Not as useful as I thought. I'm checking the cheapies in Madrid and maybe only 5%-10% of the hotels will take the coupon. Also of those that the coupon applies for, it's cheaper for me to book it at another site. For example, there's one hotel that's 50 pounds. After coupon it's 35 pounds. On another site it's 23 pounds with no coupon.

Seems that hotels in Spain don't work with it for the most part. I checked Germany and Holland as well. Most places there do work.