I've been kicking the tires with Google Instant search, and so far I think it's an improvement.
The feature,, had been known as since it was first noticed in the wild two weeks ago. Sometimes after a short pause, it retrieves results based on what you've typed as you type it, changing those results live as you add to the query.
It's like Google's search suggest feature, which offers various ways to complete your search query--but on steroids. Google argues that Instant lets people complete their searches faster, and that might well be true, but here's how I found it most powerful: I could continuously refine my search results as I went. Instead of having to search, check the results, tweak the search, check again, and so on, I could fiddle with the search terms as I went.
I found Google Instant intuitive to use and quickly grew accustomed to not having to type the Enter key at the end to initiate my search; often my typing would trail off just about the time that the query I wanted was autocompleted in gray letters with corresponding search results below. Indeed, I got in the habit of specifically avoiding hitting Enter so my search would remain live.
As is typical with the Internet at large and search specifically, though, the service works best when you're not straying far from the beaten path. Google Instant tends to nudge you where others have been before. That's handy much of the time, though it might amplify the Internet's encouragement of groupthink.
Here's an example of how Google Instant works. I typed "ex" and Expedia appeared as the top result nearly instantly. "Exch" produced a search suggestion of "exchange rates" and offered a Google calculator tool and a universal currency converter site.
It then stayed about the same until I got to "exchange rates d," when it offered "exchange rates dollar," which is what I wanted, and hitting the Tab key filled that in. At the same time, the results changed again. "Exchange rates dollar to p" suggested a completion of peso and showed the exchange rate in the search results; "exchange rates dollar to po" got to my hoped-for results, "exchange rates dollar to pound," and showed the answer at the top of the search results.
It can be distracting to have the lower part of the screen change as you type long queries, but overall, I think it's an improvement, and really, it's not that distracting if you're concentrating on typing. And even though nothing has changed compared to search suggest, you do get a more direct understanding that Google is listening to your every keystroke.
I ran into some things I found unpleasant. Using the Backspace key to refine searches sometimes, but not usually, seemed to lag. A few times there was a long wait while the search results faded nearly to white after I'd changed my search query. And even though I have a broadband connection, the service switched off on me once because of what it said was a slow connection. A drop-down box to the right of the search box switched it on again, but apparently Google Instant is sensitive to network latencies.
Of course, search ads appear also, making sure Google won't go out of business from this change. And there's a built-in "I'm feeling lucky" option for the search results that appear in the suggestions drop-down.
There are mysteries about how Google Instant works. For example, when I typed "slr purhas," the top result was Google offering that perhaps I meant "slr purchase," which is indeed where I was headed. But there was no offer to complete the search in the search bar itself, unlike with what happened trying "ipad pu" and "lawn mower pur," in which case Google inferred what I wanted and added the gray text to the search box.
But here's a funny thing: I actually am not sure how much I'll use it right now, because the vast majority of my searches take place directly from the browser (Ctrl-L/Cmd-L to get to the address bar in Chrome, and Ctrl-K/Cmd-K to get to the search bar in Firefox). Those services today offer search suggestions, but of course not Google Instant results. I'll be trying Google Instant more, but I'm not convinced I'll be going to the trouble of firing up a new search page to do so.
Overall, I'm impressed, not least because this obviously takes a lot of server horsepower and network bandwidth. It is for me an improvement, though not a revolution, in search.
I do wonder what's coming next. One possibility would be to show hybrid search results based on several of the top autocomplete options, not just the top one. Clearly Google isn't done tuning its primary profit engine.