So far I have use three exchanges and I have no problems with them regarding deposit, withdrawal and trading. These three are Poloniex, Bittrex and Coinexchange. Recently there have been some issues in this exchanges but I can only vouch with my own experience to this exchanges. You can also try other exchanges that I have not tried yet. One of this is binance as it has also large trading volume. You can search further here: https://bitcointalk.org/index.php?board=223.0 as this board is dedicated to exchanges.