I always check feedback if i need to go for unknown exchange. Sometime its necessary to go there as you told. there are bulk of bad exchange like Bittrex, bkex where i face most problem for trading. Account freeze problem, currency deposit weren't not arrived on time, withdrawal issue. Even some korean exchanges are also bad! One of those, didn’t give my fund back, no support no service. I need to go there for sell my bounty token.
Support - that's in fact the most common issue with a number of exchanges and I do love an exchange that takes the extra step to ensure that they can deal with customers complaints no matter how good their exchange platform or system is. I've experienced similar situation with deposit not getting credited and what's even more frustrating is when there's no one from the exchange's customer support team handling your issue. Anyway, when I experience such, I usually hesitate before using such exchange.