I played Portmarnock for the first time last week, in a fairly stiff wind. In response to a few of the above comments:
I would have loved to play 15 in any wind but the one I did, down wind. Cross winds or wind in the face could be dealt with; down wind required landing the ball well short of the green to have any hope of holding the surface, but the hazards short of the green (large patches of rough, bunkers) were completely hidden from the tee, making it a very difficult hole.
I found number 18 to be a fantastic finishing hole, particularly playing into the wind. The ridge crossing the fairway in the landing area created a solid division between a good drive (over the ridge) and a mediocre drive (short of the ridge); the approach shot was very challenging and the green complex incredible.
In general, although not as visually stunning as some of the other courses on the trip (RCD, Royal Portrush, Ballybunion, etc.), I found Portmarnock to be a very stern test with a very consistent atmosphere.