Tabs are also essential to my workflow. Though I could never understand why on earth in the previous (mac) version, the tabs weren't labelled correctly – the tab just gave the name of the notebook rather than the actual note, which was essentially useless for distinguishing between different notes. Given that I always had 5ish open, this was a major annoyance. I use fullscreen mode for my workflow on mac, and I use a lot of different spaces. Having all open evernote windows in separate spaces is totally impractical. You could open a separate desktop and pile up windows there (i.e. take them out of fullscreen mode), but that's still an additional space needed, and it is much slower to set up and navigate, more visually cluttered, and less user-friendly overall. I too welcome many of the new UI changes, but tabs were an essential feature for me so I will be hoping they make it back ASAP....