Tastings are expensive there, but I really enjoy
Beaulieu's reserve tasting room. I have experienced no attitude or snobbery there (even when dressed in sweaty cycling clothes).
Other, more off the beaten track wineries that I enjoy quite a bit:
William Harrison (corner of Zinfandel Lane and Silverado Trail) Killer rich Cabs, Cab Franc that despite the richness have layers of flavor and even some intriguing funkyness that I (and many of my friends) really enjoy. Plus, the tasting room manager, Rob, is a hoot!
Signorello: Silverado Trail. Fantastic views, French (Corsican) winemaker, nice cabs that I've enjoyed for some time now. Good Pinot, too.
Cade...on Howell Mountain...apppointments "required" but they fit me in because I climbed the mountain on my bicycle.

Very extracted and massive Howell Mountain cabs. Interesting Bordeaux-style Sauvignon Blanc blend. Fantastic modernist "green" architecture and the view out the window is spectacular, to say the least (the winery is at 1800 feet elevation)
If you are in Yountville for dinner or lunch, walk down the street a bit to a newly discovered favorite's tasting room,
Hope and Grace. Pleasant tasting room, great dog (Romeo) who is incredibly sweet but very shy, and some killer cabs and pinots.
Heitz Cellars. Hwy 29 in St Helena. free tasting. On weekend, they open reserve bottles that are sometimes ten to fifteen years old. They have a great American "Port" from Napa grapes. (As well as their famous cabs and a very crisp Chardonnay).
Michael Mondavi "Folio" Downtown Napa in the "Oxbow Marketplace" on First Street east of the river and in Carneros: huge lineup of wines with various labels...methinks he has a marketing background. Nonetheless, I thought some of the pourings were quite enjoyable...especially a Pinot made from grapes grown outside the back door of the Carneros facility.
Hess Not sure I am that impressed by their wines anymore, but what a facility, beautiful location, stunning building, great art collection. Redwood road immediately west of the City of Napa.
...(Humans) are unique in our capacity to construct realities at utter odds with reality. Dogs dream and dolphins imagine, but only humans are deluded. –Jacob Bacharach