Just to be clear, the road is one way and policed to ensure nobody tries to go the wrong way. The road is maintained to allow racing, so no nasty potholes or the like.
All junctions are closed (on this, the mountain section), so you cannot join or leave the road via any side roads. Join at one end, leave at the other.
There are, as Pete pointed out, risks of hitting debris etc, but no more so than on a normal track day or the Ring (in fact, there are less blind bends / crests than the Ring IIRC).
It's one of the only places where you can 'push on' on a normal road.
Maybe it's dangerous, but it beats trying to top out on the M1.....