The biggest issue I have with the new layout is that it takes away from the top, where on most monitors, it is needed.
Almost all monitors these days, whether laptop or desktop, are wide screen. Sure, some power users will rotate their desktop monitors so it is in 'Portrait' mode, but the default is 'Landscape'. If you have external monitors with rotating mounts, this works ok. But the vast majority of laptop users don't have that option. And with most printers working in height vs width (Ultimaker printers included), this is crucial. When I fire up 4.0b, I lose half of my layout area, partially because of the top area, partially because the bottom plate is a third of the way up the screen.
Having said that, if the decision of the developers is to go with this new layout, then as users, we will work around it (via plugins if need be) to make it work better for us. But I do agree with the comment about making changes for the sake of change. Look at the past in software development and review the UI changes across applications and operating Systems (even within the Windows world) and ask yourself how many of these changes were really beneficial (Windows program groups in 3.1 vs start menu in Windows 95 and up) vs new UI because we can (Microsoft BOB, Windows 8.1, Office Ribbon, etc).
Even in the Linux world (where I live and breath), we go through these changes. Sometimes they work out (KDE), sometimes you feel the full wrath of your community (Gnome2 -> Gnome3 or Unity), although working with the community together can help iron out the kinks (both Gnome3 and Unity grew to be well liked).
Don't take this as 'I hate everything about Cura changes', because if I did, I would have stayed on one version a long time ago (and wouldn't give feedback either way). Just me stating an opinion, partially backed with real world information.