I would not try Bittrex, they locked me out of my account after accepting my deposits and doing trading for a long time. I found out when I tried to get my Steem out after selling 55 SBD over ten days ago. I have 95 Steem and a bit dime (.10 BTC) stuck there and technical support hasn't answered any of my requests to close my account and refund my my coins.

This guy apparently was a validated user that got locked out:

I think that going to decentralized exchanges where we can trade directly between parties is going to become the next issue to fix. As for now I'm not sure what to suggest; I use Coinbase and had no issues.