Yes, these are stretchy.  And yes, some women swear by them.  And I used to be one of them, that is, until I got hips.  And then the one size started to cut into them, making them more noticeable and unattractive when wearing form-fitting dresses.  So if you tend to be on the curvier side, like me, you might want to take the ridiculous amount of money these skivies will set you back and find a pair that come in more sizes.