Bittrex might be ok if you are a miner seeking to dump your mined grins to hold bitcoin. I reckon Bittrex's grin wallet withdrawals might still be presently disabled.
Yesterday afternoon (afternoon in my GMT+2 timezone) both withdrawing and depositing was disabled. Let me check again...

Yep, still disabled. Hopefully this'll help support the price by locking dumping-miners out!

I think so, because no member has complained about disabled grin in bittrex. maybe most of those doing grin transactions are miners who want to throw away their coins.