For me, there are some queries that Google usually gives me better results. I couldn't tell you exactly what (mostly obscure code snippets, I think), and they're a relative minority, but sometimes I do use !g. It's not that often, though, and I'm a happy DDG user on all my computers.
I'd love to know what those 70% of your queries look like.
(One interesting observation: when first switching, I found that I liked the DDG results a lot better when I styled them to look like Google results; they felt more "right" somehow.)