I haven't had a problem with Coinbase myself, other than the fees before I went to the pro format... but that's not a service issue. I had a problem with Binance and my STEEM wallet in which I couldn't get an answer from their support team. I've opened a Bitrex account but have not funded it. I'd be interested in hearing anyone else's experiences with these or other exchanges. In any case, this is good info... Thanks!