I ran into this in Google last week and had a fit. Double quotes cannot replace what the plus sign did; it can give you exact phrases but you could use the plus sign to ensure Google included a word that they were aritrarily tossing out for results. The reason? They are coming out with searches specifically for Google+ and the plus sign in the search query will automatically make it a G+ search only. Truly sucks!
Another wonderful change to their search page: The "cached" link will no longer appear with the results but will only be available in the "Instant Preview", so you'll have to hover your mouse over the preview icon, allow it to expand to the right of the results, and then find the "cached" link in there. Of course this is "for our own good", don’t you know...
BTW, I would love to use Duck Duck Goose - the concept sounds nice, but I don’t get nearly enough search results when I use it. Hell, I may be back to Yahoo soon for my searches.