Yes, I know the Subject line is inflammatory, but I can't imagine anyone actually implementing such a radical and regressive set of changes without criticism. And yes, I describe multiple things here. It's a measure of frustration. Feel free to separate them as useful. 1. You can still tear off the address book pane to a new window, but you get a second copy of your Inbox, regardless of the folder you were reading. That's a regression. Why is the second copy of the folder there at all? 2. CTRL-SHIFT-B means "open the address book" when one is reading mail. It means "add BCC addresses" when composing a message. That causes problems for the unwary. 3. The address book opens with the address pane populated entirely with contacts. Clicking on a contact opens a display at the bottom of the pane. The display is very wasteful of space, and can block the line you just clicked. Simply scrolling the pane to reach a contact further down yields the display of the first address in the pane. The list of contacts is truncated and one has to estimate again where a contact will be. At best, it's confusing. 4. The Export... option from the Events and Tasks pulldown does nothing. 5. The Import... option form the Events and Tasks pulldown only imports a calendar file. One gets a choice using Import... from the Tools pulldown. 6. Exporting only allows creation of a ZIP file with one's complete profile, and then limits the size to 2GB. "If your current profile is larger than 2GB, we suggest you back it up by yourself." That's a regression from simply allowing export of an address book. An anonymous user on 11-30-2022 had a similar complaint as my item 1. It's posted on Mozilla Connect.