If you're not in the US, then I think it's a great exchange; if you are in the US, then I'd advise to keep them out.  I'm moving my coins out because around November 11th the 90-day promise is met and there's no guarantee what they'll do.  Will they announce a closure and give customers time to withdraw coins or will they simply lock out logins?  And what happens if you have coins on margin lending?  Right now none of these questions are answered so I'd recommend against keeping them on Bitfinex.