Windows Mobile version currently in early test stages -
Text dictation works great, but a little slow to recognize, you can tell it "Text Joey Buttafuoco" and then dictate a text message - it will transcribe it, give you a chance to edit if there's an error in transcription, and then let you send it.
Beyond that, at this point in development it is not much more than speech-based interface to bing.com
(GPS integration doesn't work yet for example, asking "where is the nearest coffee shop" searches bing.com for "where is the nearest coffee shop" without any location info.. so as you can imagine the results are not so relevant yet
But, it's not a widget, it's a native app, eventually it should be well integrated into the 6.5 system, for now Voice Command has far more features