We lived in Villanueva de la Cañada for three years, until 1996. Our house was not in the pueblo, but in the urbanizacion Villafranca del Castillo - and yes, there's a Moorish castle there. (Thanks for the link, MM - I saw my house online!!)
La Cañada pueblo has grown a lot in the past few years, and I think the opening of the university has influenced it a lot, too. It's a charming town, though not an old one.
I hear from friends still living there that the traffic to Madrid is awful in peak hours. Fernando's times are correct for non-peak hours. For example, my drive from home to work in Pozuelo de Alarcon/Aravaca was about 20 minutes long. Now I hear the same ride at 8:00 am can take an hour and a half. Madrid city would be longer by 10 minutes with no traffic. With traffic.... It all depends on when you would be traveling, and in what direction - in or out of the city. The bus goes in a special lane during peak hours, which helps. My husband rode a motorcycle in and out of the city, since he traveled during peak hours.
Still, it's a pleasant, peaceful place to live, and I really loved it. You have the great open spaces and the small town social scene, with terrazas and bars where everyone knows each other. When we were there the town had the same mayor for over 20 years - he's done such a fantastic job, the people re-elect him with an overwhelming majority at each election. Things run smoothly, and life keeps getting better there.
Fernando is also right about Majadahonda (I lived there too, for 5 years). Between Majadahonda and Pozuelo, just down the road, there's a lot going on, and they are closer than the city.