To preface, I have already submitted this feedback on the official feedback page. Here are the UI changes that I find most frustrating:
The "monochrome" look. Lacks separation of elements onscreen--visual clarity has decreased.
When hitting "return" after typing some text, there is now extra space between lines that did not use to exist (or at least the extra space was less). Why can't there be user-defined spacing options?
Bullet points--the overall size of the bullet points has been decreased to the point of tier-two bullet points looking nearly identical to tier-one. If you increase the font size enough, you can see that it's supposed to be a circle with white space. It looks like a solid dot.
I gernally like version 10. It needs more font choices, and it'd be worth the price increase if Presentation Mode was restored, but the new UI feels like a giant leap backward in usability. As I am typing in the user forums, the text is clean and very readable. Why does the desktop app look worse? The changes are so unappealing.