this is pretty awesome. I do CRISPR injections into (mouse) embryos for my work. Couldn't imagine doing it in humans, but if people are going to be doing ICSI or IVF to conceive anyway and you have got the embryos right there then why not. The only thing I would be concerned about is off-target effects, which in the mouse aren't a big deal (you breed a lot of mice in research and eventually can selectively breed out these types of things). In humans it would be a bit of a disaster. I suppose you could validate for this sort of thing in cell lines in advance of actually fixing the embryo. Still this is pretty awesome.
how much of an effect this is going to be on mankind is well.... it's probably not very much. But for individuals with the resources and means to do full sequencing to find out what if any deleterious mutations they have, it's going to basically solve potential serious problems for their kids at least. costs and technical barriers might come down enough eventually to make it more accessible, but it'll take time.