Upton's Yamato Sencha is wooooonnerful. One of the lovely things about Upton is that your tea is packed for you an comes with a label telling you how long to brew it for, and at what temperature. That specific tea, not "tea of this type."
Teavana is all marketing and very little decent tea, alas. Stash stuff is surprisingly good for a national brand, and Adiago is very nice, but also very pricy. *g*