Agreed: Napa feels a lot like a tourist trap. Though I think you only need to dial your time machine to about 12 years back to get around it. The problem is that the "name" wineries are all very crowded, charge sometimes outrageous tasting fees (they used to be free or $5 tops), sell wines at totally uncompetitive prices, and are mainly staffed by marketing interns whose only knowledge of the wines comes from what they read in the notebook this morning. Oh, and traffic sucks on the weekends and the restaurants are all too crowded, too. It's still worth visiting on occasion, especially if you've never been. Just set your expectation appropriately. And consider going to some of the lesser touristed areas in Sonoma or points west.

ETA: Two big-name Napa wineries that are worth visiting for the tours to learn a bit about how wines are made are Robert Modavi and Domaine Chandon.