In case you haven't noticed, text-based search results simply don't cut it anymore -- users are looking for people, pictures and social context. Naturally, Twitter is keeping up with the times, updating its own search bar with socially aware suggestions, previous search data and more robust results. The general search experience hasn't changed, of course, but the changes do tweak the experience for the better.
Suggested accounts, for instance, are now underlined by users you know that follow them, and simply leaving your cursor in the search field offers a preview of recent and saved searches. Results have more meat too, offering tabs for matching users and photos, as well as displaying them within the standard results stream. A revolution in social search algorithms? Probably not, but it should make it a little easier for you to keep up with the latest celebrity gossip.