For the long run ICO can be a great time to buy, but for the short or middle term buying at ICO can be a bad decision. Often the price drops after hitting the exchange and it can take a long time for price to go back up again. And sometimes the hype around a coin is to big and the price won't go back up to the price of the ICO, until now this happened with Zcash. And an example when the ICO would have been a bad decision for the short and middle term is IOTA. Now IOTA has stablelised more it's a safer buy. When you would have bought it at the ICO you would have paid more than 1/3 more then it is now.