Jetpack Comments enables your visitors to use their WordPress.com, Twitter, or Facebook accounts when commenting on your site.
Jetpack tries to match your site’s color scheme automatically, but you can make manual adjustments at the bottom of the Discussion Settings page.
Front End
Here’s what it looks like on your site once installed and setup.
So you can login using your WordPress.com, Twitter or Facebook account.
Here’s what it looks like when you are logged in.
Customize the Comment Text
Opinion
Pretty cool addition to Jetpack which saves adding or editing code to get this result.
The only problem i see with this plugin is that it seems to remove the subscribe to comments and posts that where there previously.