Following the Mango update, it is expected that the lock screen on Windows Phone 7 handsets will be active and will display cover art whenever you use your phone's music player. Another screenshot shows what looks like a new option for group messaging.
As we reported, the Mango update should also bring turn-by-turn navigation, voice-to-text SMS messaging, Bing Audio and Bing Video to handsets running on Microsoft's mobile OS. Another rumor has visual voicemail coming with the update.
source: WindowsPhoneDevPodcast via WMPoweruser