I use them too Dave and have found the "footfall" since February to be very disappointing for what I believe is a lot of money. I am also registered with many different (free) sites and have got no results from any of them, instead getting rentals from word of mouth and using Spanish sites (all our guests this year were Spanish). If your Spanish is up to scratch, or you have someone that can manage your bookings for you, I would suggest that is the best option.
At the end of the day, although we all believe our prices are reasonable, they can become very expensive once you factor in flights and car hire, etc. At least the Spanish only have to pay for their petrol.
Mark