Duck Duck Go focus on privacy issues whilst providing search results from a wide range of sources. Plugins are widely used by the company to offer searches from WolframAlpha and Wikipedia. This provides a similar services to Googles integration of Maps and various other services into it’s search results.
I found that 50% of my searches return results that satisfied my original search intentions, whilst I ended up manually going to Google for the other 50%. The more specific terms (in particular those used in software development) made up most of the failed 50%, returning vague blog articles that were nothing to do with the term.
In the end, my switch back to Google as my default search engine (in Google Chrome, my default browser) came because of an inconsistent glitch whereby if I decided to expand on my search criteria (which I often had to do on Duck Duck Go), I would be brought back to the Duck Duck Go homepage. This, quite understandable, frustrated me.
In comparison to the other search engines, Duck Duck Go seemed to work about the same (in terms of relevant search results) and it has an easy to use interface. Minus the frustrating bug I experienced, I would happily tell someone about Duck Duck Go, but Google is of course still my number one.