I think it's a decent exchange as I haven't seen or heard any scam accusations coming from it previous patronizers on the forum and outside too. Just did a google research and can't find any red flags. It also seems they have a decent security system put in place but since this is a centralized exchange your funds aren't safe with the exchange therefore irrespective of all they claim to have set up to combat hack shouldn't be trusted as even the best if the exchanges get hacks which probit isn't one yet.

I think your worries should be directed more towards the coin you purchase and not the exchange itself. Most shitcoins won't likely get listed on more popular exchange with higher liquidity so your better if exiating that trade. Probit itself has a user friendly interphase and very communicating customer service which is a good sign towards then becoming a force in the exchange business