I went to Napa for my Honeymoon in March of 07- we stayed at the Aurora Park Cottages in Calistoga. Calistogs is very pretty.. Napa itself is a little commercial if you ask me, but if you drive just a tad farther into the far end of the valley, you get a whole other view. St' Helena is nice, but spendy, but there are a lot of cute botique shops there. There is also a GREAT sushi restaurante called GO FISH.
Some wineries that I LOVED were Peju- BEautiful property and the wines are all very crisp and tasty. jessup Cellars is really a nice small place adn they have a great table wine called Table for 4. Also in Calistoga is a small family run place called Vincent Arroyo. call ahead and ask for Vincent to give you a personal tour and ask him about his dogs, JJ is his balck lab and he helps tell Vincent when the grapes are ripe. You also get to taste the wine strait from the barrels. The larger wineries are ok, cakebread, robert Mondavi, Sterling etc.. but they just dont offer the same expereince as the smaller wineries do. Have fun and it is a blast there!