The only complaints I have seen about not being able to withdraw from Polo are usually issues with the coin (wallet/network/dev team), not with the exchange. I haven't had issues withdrawing BTC at all over the last couple years.
I'm not referring to the last couple years, all the complaints exploded over the last couple months. But it could be explained by increased volume. We have to see if there continues to be problems with withdrawals over the next few months.