No clear changlog is out yet.
"It's almost difficult to say how many Windows Phone owners prefer to use Microsoft's own Bing app as opposed to Google's. Luckily for those users who happily rely on using the Bing app, there is an update that brings the app to version 5.1.2010. It's unfortunate that Verizon Windows Phone owners can't get in on this update – that's because it only is available to Windows Phones on AT&T, Sprint, and T-Mobile. It's not to say that it's a bad thing for those Verizon owners because it looks to be only a maintenance update and doesn't really offer anything exciting..........."
source: Twitter via WMExperts
I uploaded the Cab here so everyone can download...even us Verizon users that got left out
This cab is for Windows Mobile 6.1 or 6.5.