Bought these for my girlfriend, got her a Medium, she's 5'8", 145lbs.. she wore them for hot yoga tonight, said they held up fine during her workout..will update after she wears them a few more times..
This is a tight fit, but a good tight fit. Im 5'7" and 130lbs. I ordered a medium. Went right to about half inch below my belly button. Thick Fabric and wonderful print. Won't be see through during yoga and during hot yoga will keep the sweat from soaking.
Also, I wear these dancing and even just running around or meeting friends. They don't seem inappropriate if worn with a T-shirt. I usually wear leggings with a long top.