introduced me to fine Japanese Tea when I discovered their Madison Avenue, NYC store 4 years ago. If you are ever in New York, stop by. They have over 200 loose leaf selections at any given time.
I concur with Inspectoring, the red-labeled Koto no Tsuki
is one of my favorite Matcha's. Affordable and delicious.
I personally have had good luck with their Shizuoka Shincha in years past.
My Sencha recommendations are the Megami and Chiran Kanaya Midori.
They get a sublime Keemun Spring Dawn which goes quickly and is a bit pricey, but one of the most incredible black tea's I've ever tasted. You usu have to call up the store for that, as it doesn't always get put online.
The staff can be relied upon for recommendations too, as their menu changes often.