Beginning today, Internet Explorer 8 users (both IE8 Release Candidate 1 and Windows 7 versions) will notice a change in the integrated Live.com Search box.
'Answer Suggestions' has been turned on by default for all users (and testers) and essentially provides search suggestions on the fly as you type your query into the toolbar.
Yahoo's home page began providing suggestions some time ago and 'Google Suggestions', a similar service, is already live in the IE8 toolbar as well (if you added Google Search).
Tested side-by-side with Yahoo's home page (and IE8 inline Google Suggestions), the results are different across a variety of spaces, and could potentially be used by web designers to ferret out keywords that search engines are familiar with (and/or 'see' most often).
The announcement of the feature came this morning on Microsoft's Channel 10 blog.
Update 1: The Live Search Blog now has a detailed description here.
Staff edit Feb 4 5:40 AM