This is one of the tougher climbs around San Diego. It starts off steep right from the bridge, and rarely lets up all the way to the top. There are also a number of rock outcroppings along the way that brings the difficulty level up a few notches.
In many areas there is only one good line through the rocks, in other areas there are no good lines through, you just have to get through. There are some pretty good step-ups along the way as well, over both rocks and railroad ties. Some of them can be as high as 10-12 inches.
For me, the most difficult part of the climb is the left hander after the covered bench at about the 3/4 mile mark. This portion is a gnarly mix of steepness, step-ups, no good line, large loose rocks, and fatigue from the climb to this point. This part is not very long, but it's very rewarding if you can make it through.