I was about to download it, until I read their privacy policy, which I find a bit unsettling, especially the part about collecting info from your address book. Even if they claim they can not use it, I still do not feel comfortable with the idea of a company having that info. Just my personal opinion.

"We collect information that you speak or type into a vlingo text box. This is turned into statistical information which vlingo’s speech servers use to adapt to your individual voice in order to provide you with a better experience and for product improvement. We do not and can not use the information we collect from you to identify you as an individual or to identify your device.
We collect names of individuals and companies that appear in your address book, in order to provide a high quality service when you speak a contact name. We do not collect any other information associated with these names such as addresses or phone numbers. We will never use these names to contact anyone for any reason, and we have no way of associating these names with unique individuals or of linking them back to you."