The first time I visited Pacific Dunes, #8 was my least favorite hole, but I just didn't get it. I liked it a lot more the second visit. I had a pretty similar experience with #16. Just about every hole got better on my second visit.
The two holes I enjoyed the least the last time around were #9 and #18.
As I stated on the "best" thread, I've only played the course in the prevailing summer wind (ranging between very mild to whipping, but generally the same direction.) I've played the lower green on #9 more frequently than the upper green. By all accounts, I should love this hole in these conditions. I play a left-handed fade (sometimes slice) off the tee and the angled fairway plays right into my hands. The hole is actually more difficult for me to the upper green, but I enjoy that version of the hole more. The lower green has always been a "bomb the crap out of it and then see how close you can get your half-wedge or chip to the hole" kind of hole for me. That's fun, but the upper green really makes me think harder about what I want to accomplish with the tee shot. I'm probably also biased because I enjoy the upper tee on #10 (I'm probably in the minority there) and the upper green is usually connected with the upper tee.
The first time we visited, the green tee for #18 was up on the elevated box back by the tips, and I thought this hole worked much better from back there. During the second visit, the green tee was pushed up and playing from lower ground, probably the yellow tee area. This location gave me fits throughout the week. I wasn't comfortable hitting driver from this spot, but my shorter options off the tee still brought most of the trouble into play. Our group was running the ball through the fairway into the junk with 3 and 7 wood. From the back tee, I could play a shorter club and leave myself longer second and third shots, or I could break out the driver and challenge the trouble in the narrower part of the fairway.
Ballyneal - #9. I've already listed my comments on the Ballyneal thread, and others have already chimed in on this hole as well, so I won't pile on. As Tom said on the other thread, this hole defended par quite nicely. I just thought there were many more interesting holes on the course.