Use Google Voice on WP? MetroTalk is now free for the next 48 hours
Update: There is a glitch in the Marketplace, that causes the app to request payment from some users. Please wait until tomorrow, for the price change to hopefully propagate to everyone, and then try downloading again. The app will remain free until at least Thursday, and possibly longer if the problem is not resolved early enough.
Like the title says, the app is completely free for the next 48 hours. You can expect this version to be upgraded to WP8 in the coming weeks, with all the new features the OS brings.
Feel free to ask any questions.
Thanks for your support!