Google finally released their official Google Voice for iPhone app in the AppStore. It brings full GV functionality, including background notifications and full two-way communication and message sync. It's available right now US only for the time being, iPhones with iOS 3.1 or higher are supported.

As long as you've got a Google Voice account, then you shouldn't have any problems getting it running. Just hit the link here for the App Store and hit download.

[via Google Voice Blog]