Kalen,
I can think of a lot of courses that pose tougher challenges for the higher handicap than Harbour Town. As as been kind of mentioned already, the trees pose a different kind of challenge. Yes, its tough to stay between them, but its tough to get all that deep into those forests without the ball hitting a tree and the pine needles make it easy to find the ball. There's a fair amount of water too, but no worse than a number of other top courses.
The corridors are narrow, but its because of the trees, not necessarily in addition to them. I prefer this type of narrow to one that looks wide open but has nasty heather/gorse/lost ball stuff on both sides. I prefer it to a number of narrowish desert courses that don't offer much chance at recovery.
I don't love the course as much as some of Dye's other courses, but its certainly unique. Its not as strategic as many of the greats--many of the shots are dictated to a point. It requires creativity to play well--there is something to be said for that.