Ethereum is a good buy currently. The price was down mainly due to the below reasons:
1. Firstly, the introduction of a new BitMEX - ETH perpetual swap contract, which allowed traders to shorten the price of ETH with up to 100x leverage in a similar manner like the XBT (BTC) BitMEX contract. Although this has not been confirmed, this statistic has led to the speculation that the arrival of the contract allowed pessimistic investors to weigh down on the price of ETH.
2. The ICO sell-off factor, with many traders claiming that projects have begun to liquidate their war chests, that are often full of Ether, into fiat, leading to the current collapse of the market, not only ETH.
But Ethereum is still the most trusted platform for dApps and so it's still much more valuable than other similar platforms.