A lot of new coins I mined or bought, like TOP, PANDA, PND, SPA, HIRO, GRS...their prices were good before adding in Mintpal. After that, all died.
I don't see why that would be Mintpal's fault. Just invest in a coin that offers something real, something unique, and invest prior to the implementation of big innovations AND make sure the dev(s) have already proven to be competent. You'll make profits this way, trust me, I turned $20 to $3000 in less than a month when i started trading cryptos this way (and i still am making profits
).