I do not like the new web interface and therefore use the old version for the following reasons:
1. I have to do extra click to see the notebooks panel. It's is not convenient if one needs to switch from one notebook to another. With new wide screens it is not a problem to have two panels at the left. There is still plenty of room for the content. Some applications allow to pin and remain panels open if needed. I could not find this feature in Evernote.
2. The font is too large and does not seem there is a way to change it. Too little can fit on the screen.
3. There is too much white space which allows only to see so little.
4. The new interface feels slow and overloaded.
I hope they will keep the old version.