FlipToast for Windows 8 is the first Twitter Client for the Metro interface.
There is a version of FlipToast for Windows 7 and XP, but FlipToast for Metro is the first Twitter client for the touch-friendly Windows 8, which features an animated live tile. You can add a Twitter and Facebook account to the application but there is no support for multiple accounts yet.
FlipToast is targeted at the casual Twitter and Facebook user, as many powerful features are not there yet. That said, you can view comments, reply, and retweet messages from both Facebook and Twitter. You get a column for updates, news feed, photos, birthdays, inbox and "apps." It doesn't seem that FlipToast supports a column for direct messages or favorited Tweets yet.
Although FlipToast can claim the title as first Windows 8 Twitter client, there is still much work to be done. The biggest gripe I have with FlipToast is that there's no in-app browser so clicking links and even profiles will take you out of the application into Internet Explorer. It's a jarring experience and should really be integrated into the app. There are also interface quirks and inconsistencies like the fact that you can't interact with updates in the Updates column while you can in the News Feed. The games and apps in FlipToast are also nothing more than bookmarks that open up pages in Internet Explorer.
Overall, FlipToast is a good first version Twitter and Facebook client but needs a lot of polish before the official launch of Windows 8.