I've only visited the Napa Valley a few times, always as a day-trip when visiting San Francisco. It's a pretty valley, with lots of vineyards, wineries and elegant homes.
What I didn't enjoy were all the drunks on the road. Seems the wine tasting sessions at the wineries are very popular and many people swallow all the samples, rather than spitting them out. Several decades ago the wine tasting was free -- last vineyard I visited (in Walla Walla) charged for tastings, and I assume that's the case in Napa today as well.
These photos were taken at the Robert Mondavi winery.