As Mark says, it is a very aerial course, and they keep the greens quite soft. When the players are dialed in, they can score, as most of the greens are relatively flat.
The major difficulty to me is the design of the green sites, as the greens are large and segmented by deep bunkers that cut into the spaces between the "lobes" of the cloverleaf shaped greens. This makes the effective green sizes pretty small. But a player who is "in the zone," "dialed in," can go low if he keeps the tee shots in play and is very accurate with the approach shots.
For the weekend handicap golfer, it's extremely difficult for the same reasons it's relatively simple for the top golfer on his game.