It is around 530ft (150m) and no one has survived the fall, suicide or accident. so its pretty much guaranteed death with maybe a short period of time of excrutiating pain. I think at the highest point it takes 6 seconds to hit the bottom which is almost completely solid ground. It is littered with boulders which might not hamper an attempt but may result in more disfigurement and bruising. Not that a jumper would care.
I've read of a few different though close figures for attempts and successes and it seems around 1 person a week dies there and 3oo are talked down some way. Taxi drivers and other people who are in the area have learned to spot a potential jumper.
In some places the cliffs are angled at the bottom, at almost the highest point it is a sheer drop.
article from someone who visited to learn more about the suicide spot, here:
www.gettysburgreview.com