I prefer using Bitfinex. I trust the security much moreso than Cryptsy. You don't have problems with deposits and withdrawals either. I recommend all Darkcoin community members to migrate to Bitfinex.
Yes BFX is the great and very pro exchange. They have quick and quality support as well.
+101 for them.
fast but unclear interface and deposits, and will add that when making orders I don't know how much available balance I've got left, so I have to guess or do it on a calculater!