1. Google Suggest can no longer be disabled. Even if you disable Google Instant, suggestions will still be displayed.
2. You can no longer change the number of results. The interface would be less fluid if Google had to fetch 50 or 100 results every time you change your query.
3. Google Suggest no longer shows previously typed searches from Google Web History. This was a great feature for repeated queries. Marissa Mayer said last year that "40% of searches on any given day are repeat searches for a user".
4. Google Suggest no longer shows 10 suggestions. Because of space constraints, Google only displays 4 suggestions, followed by your original query.
5. The fade-in animation has been removed. This feature used to hide the navigation bar and all the links from the homepage until you moved your mouse.
6. "Search within results" is no longer available. This feature has never been useful because it didn't actually search within results. It only allowed you to add new keywords to an existing query.
7. Google's search box is not displayed at the bottom of the page. As Amit Agarwal points out, you have to scroll to the top of the page to change the query.
8. No more Wonder Wheel. Google's visualization tool allowed you to explore related searches.
9. Google removed the virtual keyboard. This feature is no longer available at Google Russia and will probably removed from all localized interfaces in the future. "Our virtual keyboard allows you to enter the precise search terms you want, regardless of the language keys on your physical keyboard. It can be helpful for people who use one of the many non-Latin script-based languages that require special characters," explains Google.
All of these features are still available if you log out or you use Google SSL, the encrypted search interface.
Can you find other missing features?
{ Thanks, Tom. }