Is there an official way to disable the Google Instant Previews feature?
FF users don’t need any add-ons or scripts to disable this.
Nor do they need to change their homepage.
In FF you can disable instant search and instant previews by modifying the about:config file.
Simple and it worked for me with no (as yet) apparent problems.
No need to install Greasemonkey as Chrome supports scripts natively
Hope this helps.
There isn't a way to permanently disable the feature at present but for now it isn't working in encrypted Google (https://www.google.com) so can be avoided.