Bottom line, you're not going to get google voice integration like it is in Android.
That said, GoVoice is a solid application.
It can access your phone's contact list and from the dialer part of the application and you can choose to text or call the person you selected from your contacts list.
You can also carry on threaded text conversations from your google voice inbox via GoVoice.
The only downside is that you don't get notifications from the App when you get a new SMS or voicemail. You can work around those limitations using google voice settings, though..
i.e. you can have it forward your SMS messages to your actual nuimber and you can reply to texts from the native SMS app and have it come from your google voice number to the recipient and you can have Google sms you or e-mail you when you get a voicemail from somebody.
It's not ideal.. but if you want ideal as far as Google Voice support, Android is the only real answer. Perhaps later the developer will be able to set information for live tiles so you can keep track that way.