14 DAY TRIAL // Google Instant seems like a great new feature and certainly brings a lot of new things, in terms of the user experience since most of the technologies were already available.
But Google Instant also takes away a few things, or at least moves them around. And it also comes with an understandable limitation to what type of search results it displays automatically.
The unofficial Google Operating System blog has a good rundown of the things which are no longer available with Google Instant.
Google Suggest can't be disabled anymore. This makes sense, there is no Google Instant without suggestions. Even if it were not to display them, all the search results would still be based on predicting what you're about to search.
By default, Google has always show 10 results per page. But you could change that to 20, 30, 50 and even 100 results per page. With Google Instant, this is no longer possible. Again, it probably makes sense, you wouldn't want to load 100 search links for each intermediary results page.
The suggestion box no longer displays items from your search history. This may be temporary, until Google manages to make everything work with the new UI. The interesting part is that Google says that the Instant results are personalized, meaning that they are based on your previous queries.
The fade-in homepage is gone with Google Instant. Now all of the links and elements on the Google homepage are visible as soon as you load the page.
There is also no search box at the bottom of the page. There are several possible reasons for this. For one, users are now less likely to scroll through the pages rather than just type a new query. Also, it would have presented a big UI problem, since the search box now incorporates suggestions as well and especially since the results are updated in real time.
One of the features that hasn't been removed, even though many are reporting that it has, is the I'm Feeling Lucky button. While the button itself just redirects to Google's logos page, there are now individual I'm Feeling Lucky links for each search suggestion.