Your physical location and past search results will now influence the order of the results you see on Bing, much like features Google has offered for years already.
For example, now if you're searching for pizza place in San Francisco, in the past you would have to type [San Francisco pizza]. Now you can simply search for [pizza] and Bing will serve results for restaurants in San Francisco.
Bing bases these results on your location, which can be set on Bing's preferences page. Just like with Google there is no opt-out, so if you don't want Bing knowing where you are (or if you want to see local results for another state) you'll have to plug in a different current location.
Bing will also use your search history to rank sites. Basically, Bing will promote a site to the top position in the SERP if it thinks you're trying to "re-find" something.
This feature is only being tested in the U.S. You can read Bing's blog post about personalized search results here.