Yahoo! Messenger Beta has officially been launched and you can try it here: Yahoo! Messenger 11.0 - Chat, Instant Message, PC Calls and More

Key features in Messenger include:-

Do more than just IM, texting, voice and video calls with your loved ones. Now you can play social games with them right within Messenger. For a start, the line-up of cool games include:
- Zynga's FishVille and Mafia Wars (coming extremely soon);
- Elex's Happy Harvest and Happy Manor;
- OMGPOP's Balloon, Pool, Draw My Thing

Connect with you friends, see their latest activities or let them know what you're up to all within Yahoo! Messenger which integrates even more of your social experiences from across the web.
- Chat with Facebook friends – Apart from Windows Live friends, you can now IM your Facebook friends within Messenger.
- Post one status to multiple social networks – Share your Messenger status simultaneously on Pulse, Facebook and Twitter, it's your choice.

Yahoo! Messenger lets you stay connected anytime, anywhere (whether desktop, the web, or mobile devices)
- Converse virtually anywhere – Start your IM conversations on your PC and continue chatting from your iPhone, Android, or any Internet-enabled device when you're on the go.
- Always be available – Stay signed in on multiple PCs simultaneously so you won't miss a message.
- Easy access to recent conversations – Retrieve recent IM conversations from any PC wherever you've signed into Messenger.