First of all, it would be hard to find a marathon course with a better combination of beauty,…read moreshade, consistent temperatures, absence of wind, and minimal hills! (Comparing to other CA marathons, S.F. has some beauty, but is very hilly. Santa Rosa is almost pancake flat, but much less shade, and often hotter. CIM is flat/net downhill, but can have unpredictable weather. Big Sur is also beautiful, but hilly and windy.)
So unless having big crowds is important to you, it's a fantastic place to lock into your pace and run a PR. Yes, there are some gently rolling ups and downs (see elevation pic), but the benefits of it being so shaded are hard to overstate.
A few other notes--it is a smaller marathon (maybe 400 runners last time?), so especially if you're running 3:15 or faster, you may or may not have many people to run with. However, during the second half of the marathon, you're also sharing the course with the HM and 10K people (who were wonderfully supportive), so especially during the second half, you won't be by yourself.
The few relatively minor challenges with this race are side effects of the remote and beautiful location. You can only get to the staging area via a single one-lane road, and marathon, HM, and 10K people are all showing up at similar times. Since many of us were driving alone, it was a lot of cars! So there we were, in the middle of the woods, sitting in stop-and-go traffic as we all drove down one lane to the parking area. (So note: don't be like me and think that you'll be able to show up at 7 a.m. for a 7:45 start! Allow a little more time. ;-)
The other thing is that cell/wi-fi service is spotty, so it takes them a while to tabulate the results and do the awards ceremony. It's not a huge deal, but plan on sticking around for a couple hours if you want your results.
All in all though, up there with Boston as one of my favorite marathon experiences, and one I'd heartily recommend.