My visit with Jonathan at Silverado shed some light on how the techniques for making Sangiovese in Napa have evolved over the years, from the mid-80s when Jack Stuart and the Millers (owners of Silverado) first went to Tuscany and decided to plant Sangiovese back home in Napa. Back then, it was the normal Cabernet treatment all the way...extracted, fussy, lots of pump-overs and punch downs to bring out more body and color. Now, at least at Silverado (and I taste this in others as well) the treatment is much more gentle, with careful in-frequent pump-overs and super-light pressings. Oak treatment is in a combination of normal 60 gal. barrels and large 500 ltr. barrels to give gentle oakiness. The 2007 Sangiovese is estate grown and is delicious. Their Super-Tuscan-style wine is called Fantasia and is a great example Napa Cal-Ital blending. It's 60/40 Sangiovese/Cabernet and it does have a real Cab character to it, but don't hold that against it. It's a lovely wine and recommended if you're looking for something different than your average Cab.
For more on other Sangiovese's in the valley, read the .PDF