I have DDG set up as the default search engine and it works quite well. I would think that I don't need to use g! about 75% of the time. When the result is from wikipedia or stack overflow or some similar popular site, DDG works alright but seems to miss specialized blogs. So if I don't find the answer on the mainstream sites I find myself doing g! more often.

75% is not bad at all and if you approach with that perspective then DDG works just great but if you think you should never have to use Google, then please wait - not sure how long.