Three months ago, I switched to using DuckDuckGo as my primary search engine. So far, I've been quite happy at how well it's worked, and now I couldn't imagine going back to
Altavista Lycos Excite LookSmart Northern Light Google.
(Rubénerd's site search, has also been served by DDG for a couple of years).
The web is littered with examples of services that based their existance on not being something else. Ello and ADN weren't Twitter. Diaspora and Google+ weren't Facebook. Few of them had/have stuck, largely because push factors alone aren't sufficient to sway changes in behaviour.
DuckDuckGo is indispensible because of pull factors. Aside from not being Google (increasingly a plus in my book), it has has features Google doesn't have, and I can't live without them now.
Take bang operators. Casey Liss did a great writeup of these, but in a nutshell they allow you to prepend tags to search queries to take you elsewhere. Typing the following will take you to Wikipedia's Bakemonogatari article:
For when DDG's results aren't enough (increasingly rare), you can even do a secured Google search which won't leak referrer information:
Answers are also a helpful addition. For example, if you search for regex, you'll get a summary of all the operators. Popular responses from the Stack Exchange network also appear inline, often saving a click.