I disagree with dr freeze and FMH1964 re Silver Oak Napa. I'm a big fan. I will note, however, that an unfortunate food pairing can really trample on the wine. So for that reason, I give it high marks but not outstanding. Spottswoode doesn't have that problem, so it's my current favorite.
I found Quintessa's wines quite overrated. When I tasted them, my palate for high-end Cal cabs was still developing, so I will have to give it another try. For now, I tend to think them overrated.
El Molino, the Chard and Pinot maker with a cult following, is certainly overrated. They're okay, but not all that, and certainly not worth what they're charging these days.
But the single-most overrated wine in the history of over-rated wines: Dom Perignon. (At least any vintage in the 1990's, the ones I've tried.) If it's free from Singapore Airlines, I'll drink it. But I'm not buying that swill. I'll take the White Star at $30/bottle over Dom any day.