One has only to look at the coinmarketcap - and everything will become clear. The coin itself is really very promising, popular and of course I think that in 2018 ethereum will grow even more in price. But a good time to buy was about two weeks ago, when the whole market was at the bottom, and ethereum - including.
even at below 900 its still a good time to buy, but less amount. dont know if we will see 700ish prices again.