Drove to the top with my family, vacationing in California, when I was a kid. Little did I know that this was my first true summit; at that time, I had a blast playing around the trails, concrete tunnel, and the aforementioned military installation mentioned by royanderson. Proximity to the Golden Gate Bridge makes it a very accessible viewpoint and a must-do (according to me) if you're in the area.
There is a cement slab left over from a military installation, with a railing, that makes a great place to sit, hang your feet, take pictures & enjoy a nice bottle of wine. Been here many times, and brought many people here, including family from Guatemala; everybody loves the view.