In Brief; extremely Flawed.
While i understand some of its security features are in place so that nothing dodgy goes on, all it does is create an air of "Vinted is the most backwards and dodgy thing i've even used", and furthermore it's usually good to know some of the vital information and elements up front.
If you downloaded the App from an add on Facebook, like i did you're in for a shock. I uploaded 6 items to sell, and it tells you there and then- when you enter a price to sell for, how much you'll actually get and how much they'll take, which is good, and uploading items using your phone is easy, but the problems started when i actually did sell something...
As someone on a lower income them most, when you sell stuff, through experience using Ebay or Etsy you get the money into your Paypal account and you can use that money to then post the package, NO! not with Vinted, they don't use Paypal either... when someone buys something from you, Vinted STORE all of the money until you send the item, you also have to send the item with a tracking number, otherwise they message you constantly informing you that you haven't posted the item, even though you have the post office reciept, and you waved it Goodbye yourself, and then if you still haven't entered a tracking number they will refund the buyer after 5 days, because OBVIOUSLY you didn't sent it. Then after flapping about this for 3 days you find out there is an "everything is okay" button that the buyer can press if they get the item and you didn't use a tracking number anyway, but that only shows itself on the 4th or last day before the threatened refund, and in the mean time you're constantly pressured for a tracking number that you clearly don't have! There's not even an option for "i don't have a tracking number" it just bullies you into entering random numbers hoping they'll work so you don't get your head flushed!!!
Also if you sell more then two items to one person you have to sell it as a "bundle" otherwise you have to post the items individually to the same person, with individual tracking numbers. They don't tell you this either! No where have i found any information about a "bundle" until they eventually e-mailed me back and informed me of it. They wont accept the same tracking number twice even if both of the items are in that bloody same package.
Oh and don't bother e-mailing for help. They reply pretty much instantly but take ages to get to the point, and end up replying to you 3-4 times before they understand your question and then they talk to you like you're the idiot, even though you've included all the links, pictures and fudging tracking numbers you can get your hands on.
If you research it online too, other complaints include Taking money out of your bank without permission, if you buy something and you want to use the money that is in your Vinted account from you selling, sometimes they don't use that they just use your bank and leave the Vinted account money sat there. But then if you try and withdraw the Money in the Vinted account to your bank it can take 5 working days- or it just doesn't acknowledge you want your money at all and it just keeps hold of it and you end up feeling like your in an eternal battle for the last Doughnut even though YOU bought them.
In short, it seems like a scam, and it probably is a scam, but its great for window shopping, i'd advise if there is anything you do want on there to contact the member, get them to take down the listing, e-mail them you're address, pay them via Paypal and do it all WITHOUT VINTED!!!
Also as a side note...STOP ASKING PEOPLE FOR SWAPS IF THE ITEM LISTED ISN'T FOR SWAPPING! THEN MOAN THAT "NO ONE WILL SWAP"- LOOK FOR THE DAMN SWAPPING ICON MORONS!