Doonbeg could not use ocean front land on holes 2-4, 7,
10-12, and 16-17 due to protected dune areas that contain a microscopic snail that feeds off the decaying root structure within the dunes, thus keeping the massive dunes intact.
In my opinion, some of the holes off the water (particularly 4--a great par 5, 11--an uphill par 3, and 17--a tough, uphill par 4) are among the best on the course.
When the water comes into view, or is in play, on holes 1,5,6,8,9,13,14,15,18, you appreciate the links qualities that much more because the ocean holes are intermingled beautifully with the inland holes.
Regarding some other comments regarding the severity of the greens, I found #2, 8, and 15 to be very penal. But on the flip side, the greens roll at a stimp of about 9 and the pros at Doonbeg will tell you that a good putter can two putt any green, from any place--kind of like Tiger Woods at the '97 Masters. Those greens have quite a bit more pitch than Doonbeg's and roll at about a 12 on the stimp.
I found Doonbeg to be everything that it was billed to be, i.e., awesome views, magnificent dunes, and a great variety of holes. I'm sure that the course will be tweaked to be made even better in coming years.