Buying ETH is gambling, plain and simple. Whether it's a good time to buy depends on whether you think that it is undervalued, not on whether the price has com down 30% in a day. I would say that there's even odds that it comes down again tomorrow. The real question is whether ETH is "worth" 10x what it was in December or January when it started taking off. No one can really answer that. DAO was ETH's first demonstration of utility, and obviously they have some work to do, but of course this doesn't mean it won't deliver in the long run. My best guess is that the price will continue to slide for a few more day, and by the time the bleeding stops 50% or more of the high price will be shed. But if the answer to the question is if ETH is a decent bet in the long run (that is, whether it's useful) is yes, then it is a good buy today, yesterday, and tomorrow, because if it does turn out to be useful, then the sky is the limit pricewise. If you're looking to pick up a quick 50%, then I think it's a terrible buy, because it's gained 1000% in a few months. That's the exact opposite of when anyone should buy any asset on a gamble.