Not to sound too repetitive, an update is available for Microsoft's Bing app for those using a Windows Phone on the Sprint, AT&T or T-Mobile network.  The new version is  5.1.2010 and you can get it by choosing the "Update Available" menu option in the old version or by pointing your mobile browser to (yeah... I know it's different than the twitter post but it's what worked for me).

No specifics on what the update covers but just off hand, it looks like a maintenance update.  If we discover anything different we'll pass it on. [via:]