My favorite part of this ride is the Petaluma-Marshall Road. The route anyway. The road itself is poor shape: bumpy and potholes and I doubt it's been repaved since the 60's. The first time I rode this part, my back starting hurting and I was like WTF? My back never hurts when riding...my butt, yes...but never my back. Anyway, I stand a lot more and spend more time dodging the hazards when I visit this part now. Oh, the route? I'm guessing the reason this road is in such bad shape, is because it's seldom used. Which, coupled with rolling hills and farm land and one short but steep hill before you race down to the coast, is pretty enjoyable.
Most of this route is good riding. You really can't go too wrong in West Marin: nice scenery, sparsely populated, usually good weather. Although, you can get caught between bathrooms/water/food if your not careful. And in the summer, it's often H-O-T!
The Mini-Paradise Loop section of this ride is a hack. I don't have a cyclocomputer, and I didn't measure the distance of the routes I was riding until I got home (via Gmaps Pedometer), so the week before I was a few miles short, so I added this section on.
An aside: The only trick for riding long distances for me is to make sure I eat and drink enough. I have a tendency not to. For the last couple of years, I couldn't ride very far without feeling like crap. I just assumed I was getting old and/or out of shape. I began not to want to ride too much. Then after not riding for the winter, Marya and I took Uncle Fester out to Samuel P. Taylor and back. Since we hadn't ridden in awhile, we brought no food. On the way back, I started feeling weak, and as we were returning through the Presidio, I had to stop. I lied down on the side of the rode and I guess I look pretty unresponsive, because a paramedics crew stopped by and I ended up in the emergency room with hypoglycemia. Anyway, that taught me to eat every 25 miles of so and now I can ride as far as like and my love of bicycling has been renewed.