I did a Sonoma-Napa loop this afternoon (Sonoma->Hwy 12->Trinity Grade->Oakville->Hwy 128->Chiles Pope Valley->back to the Silverado Trail and Napa) and the scenery is f'ing incredible. Seriously folks, hop on yer bikes and have a look, especially if you hang around till the late afternoon. I was planning to shoot some pix, but the ride was just too enjoyable (this always seems to happen to me.)
There was a bit of traffic, but you're not there to ride like your hair's on fire, are you? Slow down, and enjoy living in one of the great places on this planet.
Edit: I forgot to mention the bonus for riders: that wonderful musty-sweet-earthy smell of slowly rotting grapes. It's heady stuff!