Video chat is the prominent feature in 2.0, because now you can be making video calling to your contacts with iPhones, Android-based phones, also with their computers (Windows). And it is free to make voice calls to other YM contacts or will be charging with low-cost calls to mobile phones or landlines.
You can get cheap international calls using this YM 2.0 app but firstly you need to have a Yahoo Voice Phone Out account by signing up. And there is multitasking ability too, because it supports for iOS 4, you can let Yahoo Messenger run in the background while you take care of other business.
But unfortunately after reading several reviews, some say the quality of its poor, albeit using iPhone 4 and wi-fi. Hope it will be fixed on the next version release. But I believe this something Apple should have done a long time ago.
Download Yahoo! Messenger 2.0 for fee.