Going back a year or year-and-half ago, Yahoo was trying to get people to switch to the new view for email, but back then, it was horrible. I gave feedback several times, mainly about the "read" vs "unread" being horrible (grey shade making page unreadable), and the waste of real estate (in list mode, you could only see a few words of the mail's subject line, vs the classic mode which showed much more). The right sidebar for ads was way too big back then, like 50% bigger than classic.
Now that we are being forced to switch over, I do congratulate you on having actually listened to that feedback.
The new look is acceptable to me. Even though not as many words of subject line can be displayed in list as before, it's still quite a lot, and enough. The ad sidebar is slightly bigger than classic, but only like 10% or 20% bigger, so it's not so bad. The "read" vs "unread" indicators are pretty much same as Classic, and not using that horrible grey-shade font and background. I'm hugely relieved that even though I'm forced onto the new look, that it is at least acceptable.