The new Yahoo Mail redesign is yuck. Over all these years, the best design for Yahoo Mail was the current one, which emulated Microsoft Outlook in many ways. The new design in beta right now is a step backwards in terms of usability. The in-email chatting functionality is not very well designed either. It was slow and laggy in IE8 (don't have alternate browser choices on work computers).

Google has been criticized for many people for the left-brained, user statistics driven approach to interface design. But I think that methodology stands them in good stead. The major elements of the Gmail interface are the still the same today as they were when it was first released. A major proportion of Gmail changes over the years have been under the hood. Result: very happy users.

Compared to Google, I bet Yahoo's redesign of their email interface was influenced more by designer's 'intuition', management inputs and considerations for maximizing ad space. Result: very unhappy users.