By now, in terms of functionality[1], I mostly use DDG for the bangs, having set it as my default search engine in Firefox (keyword.URL in about:settings) so I can search using the URL bar. I caught myself doing ^T and typing "!w keywords" (to search wikipedia) on other people's computers more than once by now.
[1] I originally switched because I'm very privacy conscious, and that's still my most powerful argument for using DDG, but it's by far not the only strong argument for duckgo'ing instead of googling.
You realize that you don't have to use DDG for this, right? You can set up keyword searches in the search bar in Firefox or Chrome (don't know about other browsers) for any site, not just those that DDG supports. Then just type 'w <search>' into the location bar and hit enter for Wikipedia, for example. You can even do cool things like set up custom searches, like my 'wl' search, which automatically prepends 'list of' to any Wikpedia search.
Besides, it eliminates two keystrokes. Considering the amount of times I look up something on Wikipedia every day, I'd say that it pays itself back in spades.