In my usage over the last few years, I've come to rely on StartPage for good search results (since it's a proxy for Google). While DDG has improved over time, it still is nowhere close enough to be a Google replacement for me. I end up doing searches on DDG only to repeat the same on startpage.com to get better results. DDG still does not have time based search (where you can search for results in the past day, week, month, etc.), which is a huge disadvantage for me.
I do use both StartPage and DDG, although it's more like a 80%-19% split between these two. The remaining 1% is still on Google to get things like news, and Self-Destructing Cookies [1] helps keep things clean on that front.
[1]: https://addons.mozilla.org/en-US/firefox/addon/self-destruct...