You can visit this link to get instructions on how to use the feature and enable it on the device. http://motorola-global-portal.custhelp.com/app/answers/detail/a_id/39333/kw/voice%2Bto%2Btext/p/30%2C6720%2C7155%2C/session/L3NpZC9BV1BrSmRjaw%3D%3D/p_country_code/US/p_reference/moto_integration.ph0p
I did as you say, went to Android market, typed VOICE in the search and it listed Google Voice App. When I select it, it actually goes into the market listing, and there is no Google Voice App for download, instead it lists page after page of available apps, none of which is called explicitly Googe Voice App... There's a Goolge Voice Callback, Google Voice Intercept, Google Voice DIaler, etc... But nothing that appears to be specifically for text messages.
Yes, I do have the incredible. And I do already have the Google Voice Search, but it only searches Google, it doesn;t appear to interact with text messages... I thought this odd since a friend of mine who also has a DROID (although not the incredible) does his voice text messaging through Voice Search too... But I can only appear to search, and not do any text messaging.