Google said they removed it because it was rarely used and today, Google shared the stats on that. They said "the "+" operator in less than half a percent of all searches, and two thirds of the time, it was used incorrectly."
So instead, they added a "verbatim" option under the "More search tools" on the left hand side.
Using it will perform a literal search, and not do anything with the following:
- making automatic spelling corrections
- personalizing your search by using information such as sites you've visited before
- including synonyms of your search terms (matching "car" when you search [automotive])
- finding results that match similar terms to those in your query (finding results related to "floral delivery" when you search [flower shops])
- searching for words with the same stem like "running" when you've typed [run]
- making some of your terms optional, like "circa" in [the scarecrow circa 1963]
Matt Cutts from Google said in a Hacker News thread:
I know that a lot of people were sad that we switched from +word to "word" to do an exact match for a word.
The good news is that we're rolling out a "literal mode" that will search for exactly the words you typed. It does a verbatim match with your words, so it turns off things like spelling corrections, stemming, synonyms, optionalized terms, and so on. I think we saw multiple proposals for this on Hacker News, so thanks for the suggestion.
He then fields dozens of questions about the tool and the rational behind it.