While Google makes search much faster, Google Instant is really about showing more search results. This will have very interesting implications for consumers expectations of what they want from search, search market share, publishers, advertisers and SEO tactics.
Google Instant turns search into a real time stream of results which flow onto the screen as you type a query. With each letter you type, a whole new set of results flash by. So now, you can see many more search results than you would have otherwise. Most people never click through to the second page of search results. If it is not in the first ten blue links or really the first five or six, it might as well not be visible for most people. With Google Instant search, instead of people seeing only few results, they may now see much more, depending on how many letters they type and how far they get through each search query.
Google just found a way to increase the number of search results you see by doing nothing more than type in a word or two like you always do. Most people can scan results visually and can absorb a lot more information if it is streamed to them in this fashion rather than having to manually click through to see more results. If people get used to this, it will put pressure on Yahoo, Bing and other search engines to quickly follow suit. People go to the search engines whether they can find things more quickly. Google already dominates search market share as it is currently measured, and now by changing the method of search, makes counting queries completely outdated.
Search engine optimization will have to change and adopt to new sets of rules. Sites will need to optimize for particular letter combinations, not just entire keywords.
