I’m curious about how different
this functionality is from the FireFox’s search assist (when you use
the Google search box) or from Google’s own labs. I already use the FireFox version of this heavily.
It’s a good question, one that arises when different engines use the same name for their features (though good names are running out in that field). Google Suggest takes the most common queries beginning with the letters you enter and then shows you all the most popular queries that begin with those letters (albeit with some degree of filtering – type "se" and Sears ranks first but sex doesn’t appear, though "sexual positions" appears further down). I did a fun post on this awhile back with the Google ABCs.
Yahoo is much more complex here. First of all, it doesn’t seem to kick in until you enter three letters, accepting that with the first two it probably won’t be able to guess your intent beyond chance. More significantly though, once you get beyond that list, it then will often pull out lists of all the top words and even concepts related to that search query so you can drill down and find precisely what you’re looking for. Here, Yahoo basically becomes a search guide for you, drawing you into the long tail.
One added observation: when you use Yahoo Search assist for very commercial searches like "digital camera," you have the Assist window followed by three search ads (plus more on the right), followed by product listings from Yahoo Shopping, and then the natural search results. In my browser window, I barely saw a single natural result, making the ads much more prominent. Could this increase click-throughs on search ads?