I've been using for about 2 years now, and I highly recommend Thinx. They work best as a back up to whatever other method you prefer (cup, pad, tampon), but it's a really solid back up. Like wear-white-during-heavy-flow sort of back up. I highly recommend the high-waist, hip-hugger, and cotton bikini. I strongly advise against the sport style, which does not stay in place.
Y'all!! I have 6 pairs/varieties of Thinx period underwear and they work so great!! I no longer have to feel bad about the amount of plastic going to waste when I'm on my period. I love using a sustainable item to help save the Earth.