Generally, the greener the matcha, the truer the product. Be sure to check the ingredient label to make sure you're getting true tea -- some pre-made drinks have so many added sugars and preservatives that they barely qualify as matcha.
Beyond the pesticides, tea leaves grown in China may have high levels of lead, and Americans are becoming pretty familiar with the problems lead poses when people drink it. Consume too much, and you could end up with liver damage way worse than anything you've experienced after a boozy brunch. It's yet another reason to spend more for higher-quality matcha.
Does it live up to the hype?
If you're willing to drop a significant amount of money on your tea habit, yes! A 0.7oz can of organic Japanese matcha, for example, could cost you $12 before tax and shipping, and depending on how much you drink, that could add up quickly. But the benefits are objectively positive.