Typically when Google rolls out a change in it's technology or an algorithm it does not overtly change human search behavior. This is not true with Google Instant. Search marketers have been theorizing that above all Google Instant will dramatically effect search behavior--some have gone as far as to say it would kill SEO. (We have strongly disagreed with those points.)
It is certainly too soon to have conclusive results, as to how Instant search has changed behavior. There are some clues however. eConsultancy, took a stab at analyzing search behavior, and came up with some very interesting results. This study, it should be noted, is not going to be completely accurate.
The graphic shows an increased trend toward long-term, multiple keyword searches using Google Instant. The graphic represents eConsultancy's own search data, and it does not reflect a study using more accurate data provided by Google itself. Also, it should be noted that many users cannot access the new Instant search functionality.
eConsultancy, Google Instant has changed the way we search, 08 October 2010