I’m no expert – but the way I understand it, grinding the green tea into powder is not some modern improvement made to make the tea taste better. Rather it is a “fossil” – a survival of practices developed in the early days of tea drinking in Japan several centuries ago. It is made that way because it was always made that way, and stirring the powdered tea with the hot water is how you make tea, esp. if you are conducting a Cha-noyu.
I’ve been on the fence about ordering some of this ever since this thread came up. I need another habit like I need a hole in the head, but I took the plunge today and ordered some. Really looking forward to drinking some high end matcha at home.
It’s easy to fall down the Tea rabbit hole… High mountain Oolongs, aged Puerh… A great aged Puerh is like having mature Burgundy for breakfast.
Some fine purveyors I buy from:
Aged Oolong Tea – Red Blossom Tea Company (the 1980 Tung Ting is nice) 
http://www.houdeasianart.com/
http://floatingleaves.com/ (The winter/ spring Oolongs are epic)