This week Google began rolling out its latest search feature, Google Suggest on its homepage. The new tool, which offers suggestions when you begin typing into the blank search box, was launched to help people who have difficulty defining their queries or are bad spellers.

Google Suggest is supposed to make searching more convenient. Say you’re looking for videos of Michael Phelps’s 100 meter butterfly race. The more keywords you type in, like “Michel Phelps 100,” the better Google gets at guessing what you’re looking for. Like other search engines, Google uses its own algorithms to anticipate what you’re looking for. Google already offers a similar feature, “Did you mean?” that corrects misspelled keywords after a search is performed on the homepage. The company has also promoted the suggestion function on YouTube, the Firefox browser Google search box and its Google Labs site.

In a blog post, Jennifer Liu, a Google product manager, explained that the latest feature was “like magic.”

Both Yahoo (YHOO) and Ask.com (IACI) have been providing “magic” for some time. But so far that hasn’t  helped attract much traffic from Google .

Since Yahoo launched the Search Assist feature 13 months ago, its search market share has dropped 3%, according to comScore. Ask.com started the trend three years ago, but its percentage of search share has  remained in the single digits. Microsoft’s Live Search, the third-place search engine, does not currently offer the feature.

Enquiro, a search marketing firm that tracks the way your eyes scan search results, is skeptical that such features from really help. What matters most is the relevancy of results, notes Enquiro CEO Gord Hotchkiss.

“Yahoo Search Assist or Google Suggest are quick fixes,” he says. “All the search engines have this dilemma where they need to improve relevancy, but that requires a huge investment on the back end. The alternative is to have users do more work to define queries. But users don’t want to do more work, so the engines are using this stop-gap measure.”