This was my first time trying guayusa. I heard that it was not bitter because it doesn't have tannins like actual tea leaves do, and I definitely found that to be true. The flavor is hard to describe: it's earthy, leafy/grassy. It was fine to drink plain, but so far I have really enjoyed mixing it into other blends of loose-leaf tea that I have. (Particularly, it's nice to blend into my herbal teas to make them caffeinated).
I am loving this Guayusa Loose Leaf Tea. It is not bitter at all and I don't need any sweetener. It is gentle on the stomach. It is very high in antioxidants and highly recommend to anyone who wants an alternative to green tea.