I try to use DDG as my primary sometimes, but for me it often lets me down on those searches that you do where you know exactly what page you're after but don't have the URL bookmarked or can't be bothered finding it. I've got to the point where I'm typing long, specific strings of qualifiers (including the domain!) to try to get to e.g. the UK version of a website, and when it still doesn't show up in the first twenty-odd results of DDG I hit Google and find it with a single word.
When enough of that kind of thing happens in one day, I revert to Google and it can take me weeks to remember to try using DDG again. I like them, and I want to use them, but I can't justify hanging around when the search engine isn't finding what I'm searching for. Obviously their search capabilities aren't going to be as impressive as Google's, but it's pretty annoying (I like everything else about them, like the fact that they don't blithely ignore quotes and mutate your search string with no way of overriding).