It happens to me 5% of the time : if the results are not what you expect, you can still ask DuckDuckGo to use google, just add !g to your search (or !gm for Google Maps, or !yc for Hacker News etc.) So userful!
More here : https://duckduckgo.com/bang
Yes. This makes ddg useful as a default search engine even if you decide that you always want to use Google Search, because that you can use all the other bangs.
Being able to search "on the fly" wikipedia, youtube, google maps etc. is very valuable