Few other things I thought I should mention. If it's foggy, which it definitely can be, the views from Mt. Tam won't be so spectacular. (I was up there today though and it was great.)
Also, the descents on the Mt. Tam route are more technical (and longer) than those on the traditional route.
Finally, the stretch of Highway One from the bottom of Muir Woods Rd. to Stinson Beach can be pretty trafficky, and there's not much if any shoulder going north, which is the direction the route will be going. (I've always rode it from the other direction, and usually only do so on weekdays when there's not as much traffic.) At least driver awareness should be high though because there will be a lot of bikes on the road.
If all that sounds fine, then you will definitely like the route.