I played the golf course the fall before it opened, and a handful of times since, most recently in 2002. I don't think it has evolved all that much, really; although the first and last times I played the course there was no bunker to the right of the 12th green, but in 2000 there was a bunker with a lip so high my nine-year-old son wanted to jump off it repeatedly!
However, the work done to maintain the bunkers every winter is quite a bit more than anyone here has implied.
We had some long discussions with Dick Youngscap about the problems of migrating sand before we built our bunkers at Pacific Dunes, because we were concerned that using that style would create problems in the wind in Oregon. We decided that it was doable in Oregon because the winter rains hold the sand down, and we deliberately put irrigation water into the bunkers in the summer. Sand Hills' worst sand erosion problems are in the winter months, when there is little moisture to hold the sand in place ... hence the snow fencing and other physical barriers they put in place.
Dick's advice was that those sorts of bunkers are okay, as long as you don't get too caught up in the details of them because they are all going to change at Nature's whim. He had a good laugh at our expense [and Bill and Ben and Dan Proctor's] over how much time we spent on edging the bunkers when none of it would be the same two years later.