Anecdotally, it gives me headaches. And I know it's not the caffeine, since I can tolerate caffeine pretty well. There's something in it, some obscure compound causing the headaches. YMMV however.
+1 to this. Some other (sinensis) teas do give me headaches as well, but matcha quite consistently does even when most brewed green teas don't. Strange.
I don't enjoy the taste for long periods personally.