Not sure if everyone here will agree but Walt Mossberg of WSJ says that the new Yahoo! Mail is better than Google email and the new Windows Live Hotmail.
Walt favors Yahoo! over other web email programs because Yahoo! offers unlimited storage space, it lets you send SMS messages to cell phones, has a tabbed interface and lets you drag-n-drop email messages into mail folders just like Microsoft Outlook.
The new Yahoo! mail is no doubt a big improvement but the downside is that you have to pay an yearly fee of $20 to get your mail out of Yahoo! service - GMail POP3 access and Hotmail-Outlook Connector are free.