Bittrex verifies people within a day. In my case, it was like an hour. And I left Poloniex this summer due to many complaints from users and horrible support. I remember when they have a lot of new users and didn't want to refresh their server, I was just tired from that lagging all the time.
They're dropping US customers though :|
I noticed that a lot just begins to provide users with similar problems. What is the reason for this? Really they are covered by care of safety of users' accounts, But actually something is hidden here something else. I think that this will affect their ratings and the number of supporters of these trade exchanges.