Let's start at folders. The folders appear to just be categories and are exactly the same as a tag except an item can only be in one folder. This is a limitation, not an improvement. When the word folder is used, I expect that there is some way to nest items and other folders within a folder. As it is, I can "tag" or "categorize" items into one section.
In the UI, I found myself having to click A LOT. Creating ~4 "folders", I had to focus the dialog box to type every time I hit "new folder" and then click again because pressing the enter key did not submit the dialog form. I should not have to use my mouse to focus dialogs that pop up and I should not need to click to dismiss them.
Another UI woe is in mass item management. I imported my pocket bookmarks and now they're all in an unclassified "folder". I don't see any way to mass-select links and move them into categories. There is no world where I would waste my time moving items one by one to categorize.