In my experience it is better at "general" things. Search for a company and there will be a box describing what the company is, a specially marked box for the official homepage and a wikipedia article is often highly ranked.
However, once you start querying very specific things, it tends to fall apart. Just today I wanted to see if the a particular company utilizes any Machine Learning and searched for company-name machine learning. No top hit contained all three keywords or anything related to AI. On Google the top hit was a company research institute and contained all 3 keywords.
Single recommendation: Tiger (Animal), with a pretty picture, the life expectancy and the scientific name.
Top results: Tiger Airways, Wikipedia, Tiger Stores (a shop), WWF, Tiger Direct (another shop), Defender of Wildlife, ...
Special results "in the News": Tiger Airways, Tiger Woods.
I've been happily using DDG for almost a year now, but I still use `!g` regularly because it does get confused sometimes (point is: no search engine is perfect, but DDG makes it easy to redirect your search elsewhere.) I switched because google was pushing g+ too hard, experimenting with the presentation, customizing the result list based on my profile, and it was breaking my flow (like the popup "make google your default search engine", I get why they do it, but it required unwanted attention.) Somehow DDG convinced me that they would be less invasive.
DDG doesn't really outperform Google when it comes to search, at least not so far as I can see. I've had it set as my default for several months again.
But it does have a much nicer UI, and there are lots of searches that it does about as well as Google. For programming stuff, the !bang searches are nice (https://duckduckgo.com/bang.html) -- I can type "!mdn createElement" or "!php obscure_function" and get straight to the official docs.
For broader topics, DDG's Wikipedia preview is a nice feature, the row of embedded images across the top for famous people is handy, and for everything else, I find the search results to be more readable than Google's.
However, once you start querying very specific things, it tends to fall apart. Just today I wanted to see if the a particular company utilizes any Machine Learning and searched for company-name machine learning. No top hit contained all three keywords or anything related to AI. On Google the top hit was a company research institute and contained all 3 keywords.