I have to say it's very thin and you can see visible panty line (VPL) but I'd always wear it with a long enough top that covers my bum, otherwise I'd wear a g-string with it. The other thing I like about it is that it's not too shiny and doesn't look cheap and nasty. It's got a lovely matte finish and comfy to wear. It bunches a little at the ankles for me but that's because I'm super short. I'm a normal 6 and I got a Petite 6 in these and they fit nicely.
My work is very casual so I was able to get away with wearing these on Friday (wouldn't wear them Mon-Thu though). I dressed it up with a blouse and blazer for work.
I also wore them today to breakkie with my lover boy. I dressed it down with an oversized jumper but I did wear heels because I didn't want to look like a bum haha.
I haven't worn them enough to know what the sag factor would be like but I'd assume they would sag since they are so thin but I will report back once I've worn them a few times. Even if they do sag, at £16 (actually they cost me £14.40 because I used a 10% discount code) they're cheap enough to just buy a replacement pair. Overall I'm happy with this purchase but unfortunately won't be able to wear them for very long as they are NOT AT ALL warm and it's been rather cold in Sydney lately so I've literally been freezing my butt off.