On Tuesday, a post on the Google Mobile Blog announced that an update to Google Voice Search has been released. The update should significantly improve the app's speech recognition abililty due to the addition of personalized recognition software.
According to the Google Mobile Blog, the update also contains improvements "to name recognition and speed, especially over 3G and EDGE connections." The personalized recognition feature collects information each time you make a query, and uses that to make a speech model for every user. The more times the software is used, the more accurate it should become.
The update is available for download in the Android Market for devices running Android 2.2 or later and is only available in English for devices inside the U.S.
If this is your first time installing the software, the app will ask you whether to activate the personalized recognition. Another way to activate this ability is by going into Google Voice recognition settings and checking the box labeled "Personalized recognition."
Image from Google Mobile Blog