I've been using DuckDuckGo exclusively for several years now. But while privacy is a nice thing it has never been the No.1 reason. I just prefer their search result page design much better. I love customization options. I like !bang searches. And I almost never have been unhappy from search results.
I think if your main value is privacy and nothing more, you're lost. Most users would value privacy, but it's almost like pie in the sky thing, that's vague, hard to define, hard/impossible to prove and most importantly you don't "feel it" right away. Quite contrary, using google will give you "better" ads. But some small annoyances (like design flaws) are provable and feelable immediately and will mostly win or loose you an user.
