They redesigned the bookmark manager with a very Android-ish looking interface, where bookmark folders were represented as "blocks", similar to the Windows 8 start screen. It suffered from a few problems:

* Massive decrease in information density compared to the tree & list widgets of the "old style" bookmark manager.

* Clunky interactions. I'm pretty damn good with a computer, and I regularly ended up with bookmarks in the wrong place.

* The new interface required more clicks to get where you were going, and more clicks to perform common tasks.

Visually, the new style was more aligned with Android interfaces, but it suffered from significant UX flaws.

Thank you for the overview. Now looking at that separate "extension" that has the new behavior... I see what people are complaining about.

Maybe someone can give a better description, but you know how sometimes they redesign stuff to make it look "better" (and maybe it does look better) but it ends up being harder to work with? That happened.