To add to what I said above - I did some web searching, read through people's opinions, and it strikes me that the people who really like having a bigger-picture overview of all their notes and quickly swap between different notebooks, and move notes around between notebooks, - these people prefer the Classic interface.
The people who enjoy the new interface more strike me as people who prefer working on a smaller scale, with one note at a time.
Therefore, I would conclude that the New interface could be a very good ADDITION to the Classic, NOT a replacement. In this way, Evernote becomes an even more flexible and amazing suite of tools for writing, storing, organizing information :).
And I will add, if I know that I can switch back and forth at any time, I could see myself sometimes using the new interface, and then switching back to the Classic. In that way, I would have the best of both worlds, the best of both toolkits, and be a happier user in the end <|:)